Body Fluids & Blood Circulation

Topic: Immune System; Subtopic: Primary and Secondary Lymphoid Organs

Keyword Definitions:

• Lymphocytes: White blood cells responsible for immune responses, including B-cells and T-cells.

• Primary lymphoid organs: Organs where lymphocytes mature — bone marrow and thymus.

• Secondary lymphoid organs: Organs where mature lymphocytes encounter antigens — spleen, lymph nodes, Peyer’s patches, tonsils, etc.

• Antigen: Any substance capable of stimulating an immune response in the body.

Lead Question - 2025

After maturation, in primary lymphoid organs, the lymphocytes migrate for interaction with antigens to secondary lymphoid organ(s) / tissue(s) like:
A. Thymus    B. Bone marrow
C. Spleen    D. Lymph nodes    E. Peyer’s patches
Choose the correct answer from the options given below:
(1) B, C, D only
(2) A, B, C only
(3) E, A, B only
(4) C, D, E only

Explanation:
Lymphocytes mature in the primary lymphoid organs — thymus and bone marrow — and later migrate to secondary lymphoid organs such as the spleen, lymph nodes, and Peyer’s patches, where they encounter antigens and initiate immune responses. Thymus and bone marrow are for maturation, not antigen interaction. Answer: (4) C, D, E only.

Guessed Questions:

1. Which of the following is a primary lymphoid organ?
(1) Thymus
(2) Spleen
(3) Lymph node
(4) Tonsil
Explanation: Primary lymphoid organs are responsible for the production and maturation of lymphocytes. The thymus is where T-lymphocytes mature, making it a primary lymphoid organ. Answer: (1) Thymus.

2. Which of the following organs is responsible for the maturation of B-cells?
(1) Bone marrow
(2) Thymus
(3) Spleen
(4) Lymph nodes
Explanation: B-cells mature in the bone marrow, which also gives rise to all blood cells. Hence, bone marrow serves as both the site of lymphocyte production and B-cell maturation. Answer: (1) Bone marrow.

3. Which of the following is NOT a secondary lymphoid organ?
(1) Spleen
(2) Thymus
(3) Peyer’s patches
(4) Lymph nodes
Explanation: Secondary lymphoid organs are sites for immune response activation. Thymus is a primary lymphoid organ, while spleen, lymph nodes, and Peyer’s patches are secondary. Answer: (2) Thymus.

4. Which of the following is a site of interaction between lymphocytes and antigens?
(1) Spleen
(2) Thymus
(3) Bone marrow
(4) None
Explanation: The spleen, a secondary lymphoid organ, provides a site for immune cell interaction with antigens from the blood, leading to immune activation. Answer: (1) Spleen.

5. Which of the following structures are part of GALT (Gut Associated Lymphoid Tissue)?
(1) Peyer’s patches
(2) Thymus
(3) Lymph nodes
(4) Spleen
Explanation: Peyer’s patches are part of GALT, found in the small intestine, helping defend against intestinal pathogens. Answer: (1) Peyer’s patches.

6. The main function of the thymus is:
(1) B-cell activation
(2) T-cell maturation
(3) Antigen presentation
(4) Phagocytosis
Explanation: The thymus provides an environment for the maturation and selection of T-cells, ensuring only functional and self-tolerant T-cells are released into circulation. Answer: (2) T-cell maturation.

7. Assertion–Reason Type Question:
Assertion (A): The spleen acts as a filter for blood-borne pathogens.
Reason (R): The spleen contains both red pulp for erythrocyte destruction and white pulp for immune responses.
(1) Both A and R are true and R is the correct explanation of A
(2) Both A and R are true but R is not the correct explanation of A
(3) A is true but R is false
(4) A is false but R is true
Explanation: The spleen filters pathogens from blood and supports immune activation in its white pulp while recycling RBCs in red pulp. Both statements are correct and related. Answer: (1) Both A and R are true and R is the correct explanation of A.

8. Matching Type Question:
Match the following organs with their respective immune functions:
List I – Organ | List II – Function
A. Thymus | (i) Maturation of B-cells
B. Bone marrow | (ii) Maturation of T-cells
C. Spleen | (iii) Immune response to blood antigens
(1) A–ii, B–i, C–iii
(2) A–i, B–ii, C–iii
(3) A–iii, B–ii, C–i
(4) A–ii, B–iii, C–i
Explanation: Thymus matures T-cells, bone marrow matures B-cells, and the spleen filters blood antigens. Answer: (1) A–ii, B–i, C–iii.

9. Fill in the Blanks:
The lymphocytes that mature in the ________ become T-cells, while those that mature in the ________ become B-cells.
(1) Bone marrow, thymus
(2) Thymus, bone marrow
(3) Spleen, lymph nodes
(4) Peyer’s patches, thymus
Explanation: T-cells mature in the thymus, while B-cells mature in the bone marrow. These mature cells then migrate to secondary lymphoid organs for immune interaction. Answer: (2) Thymus, bone marrow.

10. Choose the Correct Statements:
Statement I: Lymph nodes act as filters for lymph before it returns to the bloodstream.
Statement II: Thymus is a secondary lymphoid organ.
(1) Both statements are true
(2) Only Statement I is true
(3) Only Statement II is true
(4) Both statements are false
Explanation: Lymph nodes filter lymph and facilitate antigen-lymphocyte interactions. Thymus, however, is a primary lymphoid organ. Hence, only Statement I is correct. Answer: (2) Only Statement I is true.

Topic: Circulatory System; Subtopic: Regulation of Cardiac Activities

Keyword Definitions:

• Nodal tissue: Specialized cardiac muscle tissue that generates and conducts impulses for heart contractions.

• Medulla oblongata: A part of the brainstem that controls involuntary functions like heart rate and respiration.

• Adrenal medulla: Gland producing epinephrine and norepinephrine influencing heart rate and blood pressure.

• Adrenal cortex: Outer region of adrenal gland producing steroid hormones regulating metabolism and stress response.

Lead Question – 2025

Cardiac activities of the heart are regulated by:
A. Nodal tissue
B. A special neural centre in the medulla oblongata
C. Adrenal medullary hormones
D. Adrenal cortical hormones
Choose the correct answer from the options given below:
(1) A, B and C Only
(2) A, B, C and D
(3) A, C and D Only
(4) A, B and D Only

Explanation: The heart’s rhythmic activity is primarily controlled by nodal tissue (SA and AV nodes), with additional regulation by the medulla oblongata through autonomic nerves. Adrenal medullary hormones like adrenaline enhance cardiac output. Adrenal cortical hormones play an indirect metabolic role, not direct regulation. Hence, options A, B, and C are correct.

Guessed Questions:

1. Which node acts as the natural pacemaker of the heart?
(1) AV node
(2) SA node
(3) Purkinje fibers
(4) Bundle of His

Explanation: The sinoatrial (SA) node, located in the right atrium, initiates the heartbeat by generating rhythmic electrical impulses. It sets the pace for cardiac contractions, hence called the natural pacemaker. The AV node, Purkinje fibers, and bundle of His conduct impulses but do not set the rate.

2. The Bundle of His is responsible for:
(1) Initiating cardiac impulse
(2) Conducting impulse from atria to ventricles
(3) Generating action potential in SA node
(4) Controlling heart rate

Explanation: The Bundle of His conducts electrical impulses from the AV node to the ventricular myocardium. This ensures coordinated contraction of both ventricles. It does not initiate or control impulse generation but acts as a vital conductor in the cardiac conduction system.

3. Sympathetic stimulation of the heart causes:
(1) Decrease in heart rate
(2) Increase in heart rate
(3) No change
(4) Cardiac arrest

Explanation: Sympathetic nerves release norepinephrine, which increases heart rate, cardiac contractility, and conduction velocity, preparing the body for "fight or flight" response. In contrast, parasympathetic stimulation through the vagus nerve decreases the heart rate.

4. Assertion (A): SA node is called the pacemaker of the heart.
Reason (R): It generates action potentials without external stimulation.
(1) Both A and R are true, and R is the correct explanation of A.
(2) Both A and R are true, but R is not the correct explanation of A.
(3) A is true, R is false.
(4) A is false, R is true.

Explanation: The SA node is termed the pacemaker as it generates spontaneous electrical impulses without external stimuli. This property, known as automaticity, controls rhythmic heartbeat. Thus, both statements are true, and R correctly explains A.

5. Match the following:
A. SA node → I. Pacemaker
B. AV node → II. Conducts impulse delay
C. Purkinje fibers → III. Rapid ventricular conduction
D. Bundle of His → IV. Connects atria and ventricles
Choose the correct answer:
(1) A-I, B-II, C-III, D-IV
(2) A-II, B-I, C-IV, D-III
(3) A-I, B-IV, C-II, D-III
(4) A-III, B-I, C-IV, D-II

Explanation: SA node initiates impulses (pacemaker), AV node delays conduction allowing atrial emptying, Bundle of His connects atria and ventricles, and Purkinje fibers ensure rapid impulse distribution to ventricles for coordinated contraction. Hence, option (1) is correct.

6. The pacemaker potential of SA node is due to:
(1) Inward diffusion of Na⁺
(2) Outward diffusion of K⁺
(3) Inward diffusion of Ca²⁺
(4) Both Na⁺ and Ca²⁺ influx

Explanation: The pacemaker potential results from the slow inward leak of Na⁺ ions and transient Ca²⁺ influx, gradually depolarizing the SA node membrane until threshold is reached. This triggers action potential and rhythmic heart contractions.

7. Fill in the Blanks:
The part of brain regulating the rate of heartbeat through autonomic nerves is the ________.
(1) Cerebellum
(2) Medulla oblongata
(3) Cerebrum
(4) Pons

Explanation: The medulla oblongata regulates heartbeat through its cardiac centers controlling sympathetic and parasympathetic outflow. It maintains the balance between acceleration and inhibition of cardiac activity as per physiological demands.

8. Statement I: Adrenaline increases heart rate and contractility.
Statement II: Noradrenaline decreases cardiac output.
(1) Both statements are true.
(2) Both statements are false.
(3) Statement I is true, Statement II is false.
(4) Statement I is false, Statement II is true.

Explanation: Adrenaline (epinephrine) increases heart rate, contractility, and stroke volume, thereby enhancing cardiac output. Noradrenaline also stimulates heart activity but primarily causes vasoconstriction. Hence, Statement I is true and II is false.

9. Which hormone increases the cardiac output during stress?
(1) Thyroxine
(2) Insulin
(3) Adrenaline
(4) Cortisol

Explanation: Adrenaline secreted from adrenal medulla during stress enhances cardiac output by increasing heart rate and stroke volume. It mobilizes glucose and oxygen for muscle activity, preparing the body for the “fight or flight” response.

10. Which of the following affects the rate of heart beat the least?
(1) SA node
(2) Medulla oblongata
(3) Adrenaline
(4) Adrenal cortex hormones

Explanation: Adrenal cortical hormones like cortisol influence metabolism and stress response but have minimal direct effect on heart rate. SA node, medulla oblongata, and adrenaline directly modulate heart rhythm and contractility.

Topic: Circulatory System in Amphibians; Subtopic: Venous Return and Heart Chambers in Frog

Keyword Definitions:
• Deoxygenated blood: Blood with low oxygen and high carbon dioxide content.
• Vena cava: Major vein that returns deoxygenated blood to the heart.
• Pulmonary artery: Vessel carrying deoxygenated blood from heart to lungs.
• Aorta: Major artery that carries oxygenated blood from heart to body.
• Heart chambers: Compartments of heart involved in pumping blood.
• Veins: Blood vessels that carry blood towards the heart.

Lead Question - 2025
What is the name of the blood vessel that carries deoxygenated blood from the body to the heart in a frog?
(1) Aorta
(2) Pulmonary artery
(3) Pulmonary vein
(4) Vena cava

Explanation:
In frogs, the deoxygenated blood from different body parts returns to the right atrium of the heart through the sinus venosus, which receives it from the vena cava. The vena cava thus acts as the main vein bringing deoxygenated blood back to the heart. Therefore, the correct answer is (4) Vena cava.

1. Which chamber of the frog’s heart receives oxygenated blood?
(1) Right atrium
(2) Left atrium
(3) Ventricle
(4) Sinus venosus
Explanation:
The left atrium of a frog’s heart receives oxygenated blood from the lungs through the pulmonary veins. The right atrium receives deoxygenated blood, while both atria empty into a common ventricle. Therefore, the correct answer is (2) Left atrium.

2. The heart of a frog is
(1) Two-chambered
(2) Three-chambered
(3) Four-chambered
(4) Single-chambered
Explanation:
The frog heart is three-chambered, consisting of two atria and one ventricle. The left atrium receives oxygenated blood, the right atrium receives deoxygenated blood, and the ventricle pumps mixed blood to the body and lungs. Hence, (2) Three-chambered is correct.

3. Which structure in a frog prevents the mixing of oxygenated and deoxygenated blood inside the ventricle?
(1) Conus arteriosus
(2) Sinus venosus
(3) Aortic arches
(4) Pulmonary vein
Explanation:
The conus arteriosus in a frog’s heart contains a spiral valve that directs oxygenated and deoxygenated blood into separate aortic arches, minimizing mixing. Hence, the correct answer is (1) Conus arteriosus.

4. The pulmonary vein in a frog carries
(1) Oxygenated blood from lungs to heart
(2) Deoxygenated blood from heart to lungs
(3) Deoxygenated blood from body to heart
(4) Oxygenated blood from heart to body
Explanation:
The pulmonary vein in a frog carries oxygenated blood from the lungs to the left atrium of the heart. This oxygen-rich blood later mixes slightly in the ventricle before distribution. Hence, (1) Oxygenated blood from lungs to heart is correct.

5. Which of the following blood vessels in frogs carries mixed blood?
(1) Carotid artery
(2) Pulmocutaneous artery
(3) Dorsal aorta
(4) Pulmonary vein
Explanation:
The dorsal aorta carries mixed blood from the ventricle to various body organs in frogs. It distributes blood containing both oxygenated and deoxygenated portions. Thus, (3) Dorsal aorta is correct.

6. Which of the following is responsible for collecting blood from different body organs in frogs?
(1) Carotid arch
(2) Pulmocutaneous arch
(3) Vena cava
(4) Aortic arch
Explanation:
The vena cava collects deoxygenated blood from different body organs and directs it to the sinus venosus of the heart. This blood then enters the right atrium. Hence, the correct answer is (3) Vena cava.

Assertion-Reason Question
7. Assertion (A): In frog, the heart receives both oxygenated and deoxygenated blood.
Reason (R): The frog’s heart has two atria and one ventricle.
(1) Both A and R are true, and R is the correct explanation of A.
(2) Both A and R are true, but R is not the correct explanation of A.
(3) A is true but R is false.
(4) A is false but R is true.
Explanation:
Frogs have a three-chambered heart with two atria and one ventricle. The right atrium receives deoxygenated blood, and the left atrium receives oxygenated blood, causing both types to enter a common ventricle. Hence, both statements are true and R correctly explains A. Correct answer is (1).

Matching Type Question
8. Match the following parts of the frog circulatory system with their functions:
A. Sinus venosus
B. Conus arteriosus
C. Pulmonary vein
D. Ventricle
List II – Function
(1) Receives deoxygenated blood
(2) Pumps mixed blood
(3) Prevents mixing
(4) Carries oxygenated blood
(a) A–1, B–3, C–4, D–2
(b) A–2, B–1, C–3, D–4
(c) A–4, B–1, C–2, D–3
(d) A–3, B–2, C–1, D–4
Explanation:
The sinus venosus receives deoxygenated blood, conus arteriosus prevents mixing with its spiral valve, pulmonary vein carries oxygenated blood, and ventricle pumps mixed blood. Hence, the correct match is (a) A–1, B–3, C–4, D–2.

Fill in the Blanks Question
9. The spiral valve in the conus arteriosus of frogs ensures ________.
(1) Mixing of blood
(2) Proper separation of oxygenated and deoxygenated blood
(3) Flow of blood in one direction only
(4) Circulation of blood in lungs only
Explanation:
The spiral valve in the conus arteriosus of frogs directs oxygenated and deoxygenated blood into appropriate arches and prevents their complete mixing, maintaining efficient distribution. Hence, the correct answer is (2) Proper separation of oxygenated and deoxygenated blood.

Choose the Correct Statements Question
10. Statement I: The frog heart is three-chambered.
Statement II: The left atrium of frog receives deoxygenated blood.
(1) Both statements are true
(2) Both statements are false
(3) Statement I is true, Statement II is false
(4) Statement I is false, Statement II is true
Explanation:
The frog heart has three chambers — two atria and one ventricle. The left atrium receives oxygenated blood, not deoxygenated blood. Hence, Statement I is true and Statement II is false. Correct answer: (3).

Topic: Human Heart and Circulation; Subtopic: Heart Valves and Cardiac Conducting System

Keyword Definitions:

• Tricuspid valve: Valve between the right atrium and right ventricle that prevents backflow of blood during ventricular contraction.

• Mitral (Bicuspid) valve: Valve between the left atrium and left ventricle, ensuring unidirectional blood flow.

• Semilunar valves: Valves located at the openings of the pulmonary artery and aorta, preventing backflow into ventricles.

• Sino-atrial (SA) node: Pacemaker of the heart, present in the right atrium, initiating the heartbeat and regulating rhythm.

• Cardiac cycle: Sequence of contraction and relaxation of atria and ventricles in one heartbeat.

• Ventricular systole: Phase when ventricles contract to pump blood into arteries through semilunar valves.

• Blood pressure: Force exerted by blood on arterial walls during cardiac activity.

• Pacemaker potential: Spontaneous depolarization of cardiac muscle cells in SA node that triggers heartbeat.

Lead Question - 2024 (Jhajjhar)

Match List-I with List-II.
List-I          List-II
A. Tricuspid valves        I. Guards the opening between right atrium and right ventricle
B. Sino-atrial node        II. Guards the opening between the left atrium and the left ventricle
C. Mitral valves        III. Guards the opening of right and left ventricles into pulmonary artery and aorta, respectively
D. Semilunar valves        IV. Cardiac musculature in the right upper corner of right atrium
Choose the correct answer from the options given below:

1. A-III, B-IV, C-II, D-I
2. A-II, B-I, C-IV, D-III
3. A-III, B-IV, C-I, D-II
4. A-I, B-IV, C-II, D-III

Explanation: The tricuspid valve guards the right atrium and right ventricle (I), the SA node is the natural pacemaker in the right atrium (IV), the mitral valve lies between the left atrium and left ventricle (II), and semilunar valves prevent backflow from arteries into ventricles (III). Hence, the correct match is A-I, B-IV, C-II, D-III. These valves and nodes regulate blood flow and rhythm in cardiac function.

1. Guessed Question: Which valve prevents backflow of blood into the right atrium?
1. Mitral valve
2. Tricuspid valve
3. Semilunar valve
4. Aortic valve
Explanation: The tricuspid valve, situated between the right atrium and right ventricle, prevents backflow of blood into the atrium during ventricular contraction. Its three flaps close tightly to ensure unidirectional blood flow towards the pulmonary circulation. Dysfunction may cause regurgitation or murmurs.

2. Guessed Question: The mitral valve is also called:
1. Pulmonary valve
2. Aortic valve
3. Bicuspid valve
4. Tricuspid valve
Explanation: The mitral valve, also known as the bicuspid valve, has two cusps and lies between the left atrium and left ventricle. It ensures one-way blood flow from the left atrium into the left ventricle and prevents backflow during ventricular contraction, maintaining efficient cardiac circulation.

3. Guessed Question: The pacemaker of the human heart is:
1. AV node
2. SA node
3. Purkinje fibres
4. Bundle of His
Explanation: The Sino-atrial (SA) node, located in the right atrium, generates electrical impulses that initiate the cardiac cycle. These impulses spread through atria and reach ventricles, coordinating heartbeat rhythm. Hence, it is known as the natural pacemaker of the heart.

4. Guessed Question: Semilunar valves are located at the openings of:
1. Aorta and pulmonary artery
2. Right atrium and ventricle
3. Left atrium and ventricle
4. Vena cava and aorta
Explanation: Semilunar valves guard the openings of the aorta and pulmonary artery, preventing the backward flow of blood into the ventricles during diastole. Their half-moon-shaped cusps close under pressure, maintaining efficient unidirectional blood movement through the circulatory system.

5. Guessed Question: In which part of the heart is the SA node located?
1. Upper wall of the left atrium
2. Upper wall of the right atrium
3. Interventricular septum
4. Left ventricle
Explanation: The SA node is present in the upper right atrium, near the superior vena cava. It generates electrical impulses initiating atrial contraction and sets the basic rhythm of the heartbeat. It functions as the natural pacemaker of the heart, controlling the cardiac rhythm.

6. Guessed Question: Which valve prevents backflow of blood into the left ventricle?
1. Tricuspid valve
2. Aortic valve
3. Pulmonary valve
4. Mitral valve
Explanation: The aortic valve, one of the semilunar valves, prevents the return of blood from the aorta to the left ventricle. It ensures forward movement of blood during systole and closes during diastole, maintaining pressure and preventing regurgitation into the ventricle.

7. Assertion-Reason Question:
Assertion (A): The SA node is called the pacemaker of the heart.
Reason (R): It initiates and regulates the rate of cardiac contractions.
1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. A is false, but R is true
Explanation: The SA node initiates each heartbeat and sets its rhythm by producing spontaneous electrical impulses. Therefore, both A and R are true, and R correctly explains A. It ensures synchronized contraction of the heart chambers for efficient blood pumping.

8. Matching Type Question:
Match the following cardiac components with their functions:
A. AV node – (i) Delays impulse transmission
B. SA node – (ii) Initiates heartbeat
C. Purkinje fibres – (iii) Conduct impulses to ventricular walls
D. Bundle of His – (iv) Transmits impulses from AV node
Options:
1. A-i, B-ii, C-iii, D-iv
2. A-ii, B-i, C-iv, D-iii
3. A-iv, B-i, C-ii, D-iii
4. A-iii, B-ii, C-i, D-iv
Explanation: The SA node initiates heartbeat (ii), AV node delays impulses (i) to allow atrial emptying, Bundle of His carries impulses from AV node (iv), and Purkinje fibres distribute them to ventricles (iii). Hence, A-i, B-ii, C-iii, D-iv is correct.

9. Fill in the Blanks:
The valve located between the left atrium and left ventricle is called _______.
1. Tricuspid valve
2. Pulmonary valve
3. Mitral valve
4. Aortic valve
Explanation: The mitral (bicuspid) valve separates the left atrium and left ventricle, preventing backflow during contraction. It ensures unidirectional blood flow into the ventricle, contributing to efficient cardiac output and systemic circulation control.

10. Choose the Correct Statements (Statement I & Statement II):
Statement I: Semilunar valves prevent the backflow of blood from arteries into ventricles.
Statement II: These valves are located between atria and ventricles.
1. Both statements are true
2. Both statements are false
3. Statement I is true, Statement II is false
4. Statement I is false, Statement II is true
Explanation: Semilunar valves prevent backflow from arteries into ventricles, not between atria and ventricles. Hence, Statement I is true and Statement II is false. These valves maintain unidirectional flow during cardiac cycles.

Topic: Human Heart and Cardiac Cycle; Subtopic: Electrocardiogram (ECG) and Cardiac Waves

Keyword Definitions:
• ECG (Electrocardiogram): Graphical representation of electrical activity of the heart during each cardiac cycle.
• P-wave: Represents atrial depolarisation in ECG.
• QRS Complex: Represents ventricular depolarisation.
• T-wave: Represents ventricular repolarisation.
• Depolarisation: Electrical change that initiates muscle contraction.
• Repolarisation: Restoration of resting electrical state after depolarisation.
• Sinoatrial (SA) Node: Natural pacemaker of the heart initiating the heartbeat.
• Cardiac Cycle: Sequence of events in one heartbeat including contraction and relaxation phases.
• Atrial Systole: Contraction of atria pushing blood into ventricles.
• Ventricular Systole: Contraction of ventricles ejecting blood to arteries.

Lead Question – (September 2024, Jhajjar)

In standard ECG diagram, the P-wave represents:
1. Depolarisation of the atria
2. Repolarisation of the ventricle
3. Depolarisation of the ventricle
4. End of systole

Explanation (Answer: Option 1)
In ECG, the P-wave corresponds to the depolarisation of the atria. It indicates the spread of electrical impulses from the SA node through the atria, leading to atrial contraction. This depolarisation precedes atrial systole, ensuring blood enters ventricles before ventricular contraction begins. Hence, the P-wave marks atrial electrical activation.

1. Single Correct Answer Type:
Which component of ECG represents ventricular depolarisation?
1. P-wave
2. QRS complex
3. T-wave
4. PR interval

Explanation (Answer: Option 2)
The QRS complex in ECG represents ventricular depolarisation, corresponding to the electrical impulses that initiate ventricular contraction. This complex masks atrial repolarisation due to its larger amplitude. The QRS duration reflects how quickly the ventricles depolarise and contract to pump blood into the aorta and pulmonary artery.

2. Single Correct Answer Type:
T-wave in an ECG represents:
1. Ventricular repolarisation
2. Atrial depolarisation
3. Ventricular depolarisation
4. Atrial repolarisation

Explanation (Answer: Option 1)
The T-wave represents ventricular repolarisation. It indicates the recovery phase of ventricular muscles after contraction, restoring their resting potential. A positive T-wave shows healthy ventricular repolarisation, while inverted or abnormal T-waves can indicate myocardial ischemia or electrolyte imbalance affecting cardiac rhythm stability.

3. Single Correct Answer Type:
In a normal ECG, which wave appears first?
1. QRS complex
2. P-wave
3. T-wave
4. U-wave

Explanation (Answer: Option 2)
The P-wave is the first wave of a normal ECG. It marks atrial depolarisation caused by SA node activation. The impulse travels through both atria, resulting in a small upward deflection on the ECG before the larger QRS complex that follows ventricular excitation.

4. Single Correct Answer Type:
What does the PR interval in ECG indicate?
1. Atrial depolarisation
2. Time between atrial and ventricular depolarisation
3. Ventricular repolarisation
4. Duration of one cardiac cycle

Explanation (Answer: Option 2)
The PR interval represents the time taken for electrical impulses to travel from the SA node through the atria, AV node, and into the ventricles. It measures the delay ensuring atria empty blood into ventricles before contraction. A prolonged PR interval suggests atrioventricular conduction block.

5. Single Correct Answer Type:
Which of the following is the pacemaker of the human heart?
1. AV node
2. SA node
3. Bundle of His
4. Purkinje fibres

Explanation (Answer: Option 2)
The Sinoatrial (SA) node, located in the right atrium, acts as the natural pacemaker of the heart. It initiates electrical impulses that spread through the atria causing the P-wave. Its automatic rhythmic activity sets the basic heart rate, coordinating the timing of cardiac contractions.

6. Single Correct Answer Type:
The QRS complex is absent in which cardiac condition?
1. Atrial fibrillation
2. Ventricular block
3. SA node failure
4. Complete heart block

Explanation (Answer: Option 4)
In a complete heart block, the electrical impulse from the atria fails to reach the ventricles. Consequently, the QRS complex may be absent or abnormally delayed. The atria and ventricles beat independently, indicating total AV conduction failure requiring pacemaker intervention.

7. Fill in the Blanks Type:
In ECG, the ________ represents ventricular repolarisation.
1. P-wave
2. T-wave
3. QRS complex
4. PR interval

Explanation (Answer: Option 2)
The T-wave denotes ventricular repolarisation. After depolarisation and contraction, the ventricles recover their resting electrical potential. A normal upright T-wave reflects proper ventricular recovery, whereas inversion or flattening may indicate cardiac ischemia or electrolyte disturbances.

8. Matching Type:
Match the following:
A. P-wave — (i) Atrial depolarisation
B. QRS complex — (ii) Ventricular depolarisation
C. T-wave — (iii) Ventricular repolarisation

1. A-(i), B-(ii), C-(iii)
2. A-(ii), B-(i), C-(iii)
3. A-(iii), B-(ii), C-(i)
4. A-(i), B-(iii), C-(ii)

Explanation (Answer: Option 1)
The P-wave corresponds to atrial depolarisation, the QRS complex to ventricular depolarisation, and the T-wave to ventricular repolarisation. This sequence represents normal cardiac electrical activity during one heartbeat, ensuring efficient heart pumping and rhythmic cycles.

9. Assertion-Reason Type:
Assertion (A): QRS complex represents ventricular depolarisation.
Reason (R): Ventricular depolarisation initiates ventricular systole.

1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) true but (R) false.
4. (A) false but (R) true.

Explanation (Answer: Option 1)
The QRS complex represents ventricular depolarisation, triggering ventricular muscle contraction known as systole. The depolarisation spreads through the Purkinje fibres initiating coordinated contraction of both ventricles. Hence, both statements are true and Reason correctly explains Assertion.

10. Choose the Correct Statements (Statement I & II):
Statement I: P-wave indicates atrial depolarisation.
Statement II: QRS complex represents atrial repolarisation.

1. Both statements are true
2. Both statements are false
3. Statement I true, Statement II false
4. Statement I false, Statement II true

Explanation (Answer: Option 3)
The P-wave denotes atrial depolarisation. The QRS complex represents ventricular depolarisation, not atrial repolarisation. Atrial repolarisation occurs but is masked by the large QRS complex. Hence, Statement I is true while Statement II is false.

Topic: Circulatory System; Subtopic: Chambers of Heart in Different Vertebrates

Keyword Definitions:

• Chambered Heart: The heart divided into auricles and ventricles for separation of oxygenated and deoxygenated blood.

• Bufo: A genus of toads belonging to Amphibia, showing a three-chambered heart.

• Alligator: A reptile with an incompletely divided four-chambered heart showing partial mixing of blood.

• Struthio: The ostrich, a bird possessing a four-chambered heart.

• Calotes: A garden lizard having a three-chambered heart typical of reptiles.

• Rana: A frog with a three-chambered heart (two atria and one ventricle).

Lead Question - 2024 (Jhajjhar)

Which of the following group of animals have three chambered heart?
1. Bufo, Alligator, Struthio
2. Chameleon, Hyla, Calotes
3. Crocodilus, Pavo, Clarias
4. Exocoetus, Hemidactylus, Rana

Explanation: Amphibians like Rana and reptiles like Chameleon and Calotes have a three-chambered heart consisting of two atria and one ventricle. Birds and crocodiles possess a four-chambered heart, whereas fish have a two-chambered one. Therefore, the correct answer is option 2: Chameleon, Hyla, Calotes. This adaptation helps in partial double circulation.

Guessed Questions:

1. Which of the following animals has a four-chambered heart?
A. Crocodile
B. Frog
C. Lizard
D. Salamander

Explanation: Among reptiles, only the crocodile possesses a four-chambered heart, providing complete separation of oxygenated and deoxygenated blood. It is an evolutionary advancement towards efficient oxygen supply. Thus, the correct answer is A. Crocodile, a unique reptile showing complete double circulation like mammals and birds.

2. In which group of vertebrates is the heart two-chambered?
A. Fishes
B. Amphibians
C. Reptiles
D. Birds

Explanation: Fishes have a two-chambered heart consisting of one atrium and one ventricle. Blood passes through the heart only once during each circulation, a pattern called single circulation. This limits oxygen availability, hence lower metabolic rates. Therefore, the correct answer is A. Fishes.

3. Which of the following shows incomplete double circulation?
A. Frog
B. Crocodile
C. Bird
D. Mammal

Explanation: In frogs, the heart is three-chambered, causing partial mixing of oxygenated and deoxygenated blood, termed incomplete double circulation. It allows survival both in water and land by adjusting oxygen needs. Thus, the correct answer is A. Frog.

4. Which one of the following has a three-chambered heart with incomplete partition?
A. Snake
B. Fish
C. Mammal
D. Bird

Explanation: Snakes, like most reptiles, have a three-chambered heart with two atria and one ventricle partially divided by an incomplete septum. This structure allows partial mixing of oxygen-rich and oxygen-poor blood. Hence, the correct answer is A. Snake.

5. Which statement about amphibian heart is correct?
A. Two auricles and one ventricle
B. Two ventricles and one auricle
C. One auricle and one ventricle
D. Two auricles and two ventricles

Explanation: The amphibian heart comprises two auricles and one ventricle, allowing oxygenated and deoxygenated blood to mix partially. This adaptation supports their dual life (aquatic and terrestrial). Therefore, the correct answer is A. Two auricles and one ventricle.

6. Which type of circulation is present in amphibians?
A. Single circulation
B. Double but incomplete circulation
C. Double complete circulation
D. Open circulation

Explanation: Amphibians like frogs show double but incomplete circulation where blood passes twice through the heart during one cycle, but oxygenated and deoxygenated blood partially mix in the ventricle. Hence, the correct answer is B. Double but incomplete circulation.

Assertion-Reason Type:
Assertion (A): Amphibians show incomplete double circulation.
Reason (R): They have a three-chambered heart with one ventricle where oxygenated and deoxygenated blood mix.
1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, R is false
4. A is false, R is true

Explanation: Amphibians possess a three-chambered heart, causing partial mixing of oxygenated and deoxygenated blood in the ventricle, hence incomplete double circulation. Thus, both A and R are true, and R correctly explains A. Therefore, the correct answer is option 1.

Matching Type:
Match the animal with its number of heart chambers:
A. Fish
B. Frog
C. Crocodile
D. Bird
I. 2
II. 3
III. 4

Options:
1. A-I, B-II, C-III, D-III
2. A-I, B-II, C-III, D-III
3. A-I, B-II, C-III, D-III
4. A-I, B-II, C-III, D-III

Explanation: Fish has a two-chambered heart, frog has a three-chambered heart, while crocodile and birds have a four-chambered heart. The correct matching is A-I, B-II, C-III, D-III, indicating progressive complexity in circulation from fishes to birds. Hence, option 1 is correct.

Fill in the Blanks:
In reptiles like snakes and lizards, the heart has ___ chambers.

Options:
A. Two
B. Three
C. Four
D. Five

Explanation: Reptiles (except crocodiles) possess a three-chambered heart having two atria and one ventricle, which allows partial separation of oxygenated and deoxygenated blood. This adaptation supports terrestrial life. Hence, the correct answer is B. Three.

Choose the Correct Statements (Statement I & II):
Statement I: Crocodiles have a four-chambered heart.
Statement II: Amphibians have a completely divided ventricle.

Options:
1. Both statements are true
2. Both statements are false
3. Statement I is true, Statement II is false
4. Statement I is false, Statement II is true

Explanation: Crocodiles are unique reptiles with a four-chambered heart, enabling complete separation of blood, while amphibians have a single ventricle not divided completely. Therefore, Statement I is true and Statement II is false, making option 3 correct.

Topic: Electrocardiogram (ECG); Subtopic: Interpretation of ECG Waves

Keyword Definitions:

• Electrocardiogram (ECG): A graphical recording of the electrical activity of the heart during a cardiac cycle.

• P wave: Represents depolarisation of atrial muscles before atrial contraction.

• QRS complex: Represents depolarisation of the ventricles leading to ventricular contraction.

• T wave: Represents repolarisation of ventricles.

• T–P interval: Represents the period when the heart muscles are electrically silent and relaxed.

• Depolarisation: Loss of polarity across a membrane during excitation of muscle or nerve cells.

• Repolarisation: Restoration of the resting potential after depolarisation.

Lead Question – 2024
Match List I with List II:

List I          List II
A. P wave          I. Heart muscles are electrically silent
B. QRS complex      II. Depolarisation of ventricles
C. T wave          III. Depolarisation of atria
D. T–P gap        IV. Repolarisation of ventricles

(1) A–III, B–II, C–IV, D–I
(2) A–II, B–III, C–I, D–IV
(3) A–IV, B–II, C–I, D–III
(4) A–I, B–III, C–IV, D–II

Explanation: ECG shows the electrical activity of the heart. P wave indicates atrial depolarisation, QRS complex indicates ventricular depolarisation, T wave indicates ventricular repolarisation, and the T–P interval shows the resting phase when the heart muscles are electrically silent. Hence, the correct match is A–III, B–II, C–IV, D–I. Answer: (1)

Guessed Questions:

1. The P wave of ECG represents:
(1) Depolarisation of ventricles
(2) Depolarisation of atria
(3) Repolarisation of ventricles
(4) Repolarisation of atria
Explanation: The P wave arises due to the depolarisation of atrial muscle fibres just before atrial contraction. It represents electrical excitation initiating atrial systole. Any abnormality in the P wave may indicate atrial enlargement or conduction defects. Answer: (2)

2. Which part of ECG corresponds to ventricular depolarisation?
(1) P wave
(2) QRS complex
(3) T wave
(4) P–R interval
Explanation: The QRS complex represents depolarisation of the ventricles, leading to ventricular contraction. It is usually the largest wave in ECG because the ventricles have more muscle mass than atria. Answer: (2)

3. The T wave in ECG denotes:
(1) Depolarisation of atria
(2) Repolarisation of ventricles
(3) Repolarisation of atria
(4) Depolarisation of ventricles
Explanation: The T wave represents ventricular repolarisation, restoring the resting potential after contraction. A tall T wave may suggest hyperkalemia, while a flattened T wave may indicate ischemia. Answer: (2)

4. The T–P interval of ECG indicates:
(1) Atrial depolarisation
(2) Ventricular depolarisation
(3) Electrical inactivity
(4) Atrial repolarisation
Explanation: The T–P interval represents the time during which all chambers of the heart are in diastole, and the heart muscles are electrically silent. It reflects complete relaxation of cardiac muscles. Answer: (3)

5. Which component of ECG is longest in duration?
(1) P wave
(2) QRS complex
(3) T wave
(4) P–R interval
Explanation: The P–R interval represents the time between the onset of atrial depolarisation and ventricular depolarisation. It is longer than individual waves and indicates conduction through the AV node. Answer: (4)

6. Which wave disappears in atrial fibrillation?
(1) P wave
(2) QRS complex
(3) T wave
(4) U wave
Explanation: In atrial fibrillation, there is chaotic atrial activity causing absence of distinct P waves in ECG. The QRS complex and T wave remain, but rhythm becomes irregular due to uncoordinated atrial depolarisation. Answer: (1)

Assertion-Reason Question
Assertion (A): QRS complex represents ventricular depolarisation.
Reason (R): Depolarisation leads to contraction of cardiac muscles.
(1) Both A and R are true, and R is the correct explanation of A
(2) Both A and R are true, but R is not the correct explanation of A
(3) A is true, but R is false
(4) A is false, but R is true
Explanation: Depolarisation of ventricles results in the QRS complex and causes muscle contraction during systole. Hence both statements are correct, and the reason correctly explains the assertion. Answer: (1)

Matching Type Question
Match the following cardiac events with ECG components:
A. Atrial depolarisation → I. P wave
B. Ventricular depolarisation → II. QRS complex
C. Ventricular repolarisation → III. T wave
D. Relaxation period → IV. T–P interval
(1) A–I, B–II, C–III, D–IV
(2) A–II, B–I, C–III, D–IV
(3) A–I, B–III, C–II, D–IV
(4) A–II, B–IV, C–III, D–I
Explanation: Each part of the ECG corresponds to a specific cardiac event: P wave to atrial depolarisation, QRS complex to ventricular depolarisation, T wave to ventricular repolarisation, and T–P interval to the resting phase. Answer: (1)

Fill in the Blanks Question
In ECG, the _______ wave corresponds to ventricular repolarisation.
(1) P
(2) QRS
(3) T
(4) U
Explanation: The T wave represents ventricular repolarisation, which restores the resting potential after depolarisation. It indicates electrical recovery of ventricles before the next heartbeat. Answer: (3)

Choose the Correct Statements Question
Statement I: The QRS complex represents ventricular depolarisation.
Statement II: The T wave represents atrial depolarisation.
(1) Both statements are correct
(2) Both statements are incorrect
(3) Statement I is correct, Statement II is incorrect
(4) Statement I is incorrect, Statement II is correct
Explanation: The QRS complex indeed represents ventricular depolarisation. However, atrial depolarisation is represented by the P wave, not the T wave. The T wave corresponds to ventricular repolarisation. Answer: (3)

Topic: Human Heart and Cardiac Function; Subtopic: Conduction System of the Heart

Keyword Definitions:

• SA Node: Sinoatrial node is the pacemaker of the heart located in the right atrium that initiates the heartbeat.

• AV Node: Atrioventricular node receives impulses from the SA node and passes them to the ventricles through the bundle of His.

• AV Bundle (Bundle of His): A collection of specialized cardiac muscle fibers that transmit impulses from the AV node to the ventricles.

• Purkinje Fibres: Fine conducting fibers that spread the impulse to ventricular muscles, causing contraction.

• Bundle Branches: Pathways that carry impulses through the interventricular septum to both ventricles.

Lead Question - 2024
Following are the stages of pathway for conduction of an action potential through the heart:
A. AV bundle  B. Purkinje fibres  C. AV node  D. Bundle branches  E. SA node
Choose the correct sequence of pathway from the options given below:
(1) A-E-C-B-D
(2) B-D-E-C-A
(3) E-A-D-B-C
(4) E-C-A-D-B

Explanation: The correct answer is (4) E-C-A-D-B. The sequence of cardiac impulse conduction is SA node → AV node → AV bundle (Bundle of His) → bundle branches → Purkinje fibres. The SA node initiates the impulse, the AV node delays it slightly, and the remaining conduction structures distribute it throughout the ventricles for synchronized contraction.

1. Which part of the heart acts as the natural pacemaker?
(1) AV node
(2) SA node
(3) Purkinje fibers
(4) Bundle branches
Explanation: The correct answer is (2) SA node. The sinoatrial node generates rhythmic electrical impulses that set the pace of cardiac activity. Located in the right atrium, it ensures coordinated atrial contraction followed by ventricular excitation, maintaining regular heartbeat essential for proper blood circulation throughout the body.

2. Which of the following ensures coordinated ventricular contraction?
(1) Purkinje fibers
(2) SA node
(3) AV node
(4) Semilunar valves
Explanation: The correct answer is (1) Purkinje fibers. These fibers spread the electrical impulse rapidly across the ventricular walls, ensuring that both ventricles contract simultaneously. This coordination helps maintain efficient pumping of blood into the pulmonary artery and aorta during systole, promoting uniform cardiac output and effective circulation.

3. The delay in the transmission of cardiac impulse occurs at:
(1) SA node
(2) Purkinje fibers
(3) AV node
(4) Bundle branches
Explanation: The correct answer is (3) AV node. The AV node introduces a short delay before passing the impulse to the ventricles, allowing the atria to complete contraction and empty blood into the ventricles. This ensures efficient cardiac filling and synchronization of atrial and ventricular contractions during the cardiac cycle.

4. The conduction system of the heart is made up of:
(1) Neurons
(2) Modified cardiac muscle fibers
(3) Smooth muscles
(4) Skeletal muscle fibers
Explanation: The correct answer is (2) Modified cardiac muscle fibers. The heart’s conduction system includes SA node, AV node, bundle of His, bundle branches, and Purkinje fibers. These specialized fibers conduct impulses rapidly but are not neurons. Their muscular origin ensures both excitability and contractility unique to cardiac tissue.

5. The bundle of His is located in the:
(1) Right atrium
(2) Interventricular septum
(3) Left ventricle
(4) Pulmonary artery
Explanation: The correct answer is (2) Interventricular septum. The bundle of His extends from the AV node into the septum between ventricles, dividing into right and left bundle branches. It transmits impulses to Purkinje fibers, ensuring synchronized ventricular contraction necessary for effective pumping of blood into major arteries.

6. The main function of the AV node is to:
(1) Initiate the heartbeat
(2) Delay conduction for proper ventricular filling
(3) Act as a barrier between atria and ventricles
(4) Generate action potential
Explanation: The correct answer is (2) Delay conduction for proper ventricular filling. The AV node slows down the impulse from the SA node to allow atria to contract completely. This ensures blood flows efficiently into ventricles before they contract, preventing overlap of atrial and ventricular systole for effective cardiac rhythm.

7. Assertion-Reason Type Question:
Assertion (A): SA node acts as the pacemaker of the heart.
Reason (R): It generates impulses that initiate each cardiac cycle.
(1) Both A and R are true, and R is the correct explanation of A.
(2) Both A and R are true, but R is not the correct explanation of A.
(3) A is true, but R is false.
(4) A is false, but R is true.
Explanation: The correct answer is (1). The SA node initiates impulses spontaneously due to automatic depolarization, establishing the rhythm of the heart. This makes it the natural pacemaker responsible for maintaining consistent heartbeat frequency and ensuring coordinated cardiac contraction during each cycle of activity.

8. Matching Type Question:
Match the following cardiac components with their functions:
A. SA node  I. Initiates cardiac impulse
B. AV node  II. Delays impulse transmission
C. Bundle branches  III. Carry impulses to ventricles
D. Purkinje fibers  IV. Stimulate ventricular muscle contraction
(1) A-I, B-II, C-III, D-IV
(2) A-II, B-I, C-IV, D-III
(3) A-IV, B-III, C-II, D-I
(4) A-I, B-III, C-IV, D-II
Explanation: The correct answer is (1). The SA node initiates cardiac impulse, the AV node delays conduction, bundle branches transmit signals through the septum, and Purkinje fibers deliver impulses to the ventricular myocardium, ensuring rapid and coordinated muscle contraction vital for efficient heart pumping.

9. Fill in the Blanks:
The electrical activity of the heart begins at the ________ and ends at the ________.
(1) AV node, Purkinje fibers
(2) SA node, Purkinje fibers
(3) Bundle branches, SA node
(4) AV bundle, Purkinje fibers
Explanation: The correct answer is (2) SA node, Purkinje fibers. The conduction pathway starts with impulse generation in the SA node, proceeds through the AV node, bundle of His, and bundle branches, and ends at Purkinje fibers. This sequential activation ensures synchronized contraction and effective ejection of blood.

10. Choose the Correct Statements:
Statement I: SA node is located in the wall of the left atrium.
Statement II: Purkinje fibers carry impulses to the ventricular muscle.
(1) Both statements are true.
(2) Both statements are false.
(3) Statement I is false, Statement II is true.
(4) Statement I is true, Statement II is false.
Explanation: The correct answer is (3). The SA node lies in the wall of the right atrium near the superior vena cava. Purkinje fibers efficiently distribute electrical impulses through ventricular walls, triggering rapid, uniform muscle contraction essential for coordinated cardiac output during each heartbeat.

Topic: Blood and Immunity; Subtopic: White Blood Cells (Leukocytes)

Keyword Definitions:

• Leukocytes: White blood cells involved in defense against infections and foreign particles.

• Eosinophils: Granulocytes involved in combating parasitic infections and allergic reactions.

• Lymphocytes: Agranulocytes responsible for adaptive immunity, including B and T cells.

• Neutrophils: Granulocytes that are first responders to bacterial infection and inflammation.

• Monocytes: Agranulocytes that differentiate into macrophages and dendritic cells for phagocytosis.

• Percentage of WBC: Normal proportion of each leukocyte type in blood.

• Granulocytes: WBCs containing granules, including neutrophils, eosinophils, basophils.

• Agranulocytes: WBCs without visible granules, including lymphocytes and monocytes.

• Phagocytosis: Process of engulfing and digesting pathogens or debris.

• Adaptive Immunity: Immunity that is specific and has memory, mediated by lymphocytes.

• Innate Immunity: Non-specific defense mechanisms including neutrophils and monocytes.

Lead Question - 2023 (Manipur)

Match List - I with List - II

List-I  List-II

(A) Eosinophils — (I) 6-8%

(B) Lymphocytes — (II) 2-3%

(C) Neutrophils — (III) 20-25%

(D) Monocytes — (IV) 60-65%

Choose the correct answer from the options given below:

Options: (A) (B) (C) (D)

1. IV I II III

2. IV I III II

3. II III IV I

4. II III I IV

Explanation:

In normal human blood, neutrophils form the largest proportion of leukocytes (60-65%), followed by lymphocytes (20-25%), monocytes (6-8%), and eosinophils (2-3%). Correct matching: Eosinophils → II, Lymphocytes → III, Neutrophils → IV, Monocytes → I. Understanding leukocyte distribution is important for diagnosing infections, immune disorders, and hematological conditions. White blood cell differential counts help identify abnormal immune responses, inflammation, and hematopoietic abnormalities. Hence, the correct option is 4.

1. Single Correct Answer MCQ:

Which WBC is primarily responsible for phagocytosis during bacterial infections?

1. Eosinophils

2. Neutrophils

3. Lymphocytes

4. Basophils

Explanation:

Neutrophils are first responders and perform phagocytosis to engulf bacteria and debris. Eosinophils combat parasites, lymphocytes mediate adaptive immunity, basophils release histamine. Correct answer is 2.

2. Single Correct Answer MCQ:

Which leukocytes are majorly involved in adaptive immunity?

1. Neutrophils

2. Eosinophils

3. Lymphocytes

4. Monocytes

Explanation:

Lymphocytes mediate adaptive immunity, producing antibodies (B cells) and cytotoxic responses (T cells). Neutrophils and eosinophils belong to innate immunity. Monocytes differentiate into macrophages. Correct answer is 3.

3. Single Correct Answer MCQ:

Which leukocyte increases in parasitic infections and allergies?

1. Neutrophils

2. Basophils

3. Eosinophils

4. Monocytes

Explanation:

Eosinophils combat parasitic infections and mediate allergic reactions by releasing toxic granules. Neutrophils target bacteria, basophils release histamine, monocytes phagocytose pathogens. Correct answer is 3.

4. Single Correct Answer MCQ:

Monocytes differentiate into:

1. Lymphocytes

2. Macrophages

3. Neutrophils

4. Basophils

Explanation:

Monocytes are agranulocytes that differentiate into macrophages and dendritic cells, which perform phagocytosis and antigen presentation. Lymphocytes, neutrophils, basophils have different origins. Correct answer is 2.

5. Single Correct Answer MCQ:

Normal percentage of neutrophils in human blood is:

1. 2-3%

2. 6-8%

3. 20-25%

4. 60-65%

Explanation:

Neutrophils form the largest fraction of leukocytes, approximately 60-65%, followed by lymphocytes, monocytes, and eosinophils. Correct answer is 4.

6. Single Correct Answer MCQ:

Which WBC is smallest in percentage in normal blood?

1. Neutrophils

2. Monocytes

3. Eosinophils

4. Lymphocytes

Explanation:

Eosinophils are the least abundant, ~2-3% of WBCs. Monocytes ~6-8%, lymphocytes 20-25%, neutrophils 60-65%. Correct answer is 3.

7. Assertion-Reason MCQ:

Assertion (A): Lymphocytes are responsible for antibody production.

Reason (R): B cells differentiate into plasma cells that secrete antibodies.

1. Both A and R are true and R explains A

2. Both A and R are true but R does not explain A

3. A is true but R is false

4. Both A and R are false

Explanation:

a subtype of lymphocytes differentiate into plasma cells, which produce antibodies, thus providing adaptive immunity. Both statements are true and R correctly explains A. Correct answer is 1.

8. Matching Type MCQ:

Match WBC with its normal percentage:

A. Neutrophils — (i) 60-65%

B. Lymphocytes — (ii) 20-25%

C. Monocytes — (iii) 6-8%

D. Eosinophils — (iv) 2-3%

1. A-(i), B-(ii), C-(iii), D-(iv)

2. A-(ii), B-(i), C-(iv), D-(iii)

3. A-(iii), B-(iv), C-(ii), D-(i)

4. A-(iv), B-(iii), C-(i), D-(ii)

Explanation:

Correct percentages: Neutrophils 60-65% (i), Lymphocytes 20-25% (ii), Monocytes 6-8% (iii), Eosinophils 2-3% (iv). Correct option is 1.

9. Fill in the Blanks MCQ:

The WBC type that differentiates into macrophages is ______.

1. Lymphocytes

2. Monocytes

3. Neutrophils

4. Eosinophils

Explanation:

Monocytes differentiate into macrophages in tissues to perform phagocytosis and antigen presentation. Lymphocytes mediate adaptive immunity, neutrophils and eosinophils are granulocytes. Correct answer is 2.

10. Choose the correct statements MCQ:

Statement I: Neutrophils are the most abundant WBC.

Statement II: Eosinophils are mainly involved in bacterial defense.

1. Statement I only

2. Statement II only

3. Both statements are true

4. Both statements are false

Explanation:

Statement I is correct: neutrophils are the most abundant WBCs (~60-65%). Statement II is incorrect: eosinophils target parasites and mediate allergic responses, not primarily bacterial defense. Hence, only Statement I is correct, option 1.

Topic: Cardiovascular System; Subtopic: Electrocardiogram (ECG)

Keyword Definitions:

• Electrocardiogram (ECG): A recording of the electrical activity of the heart over time using electrodes placed on the skin.

• P-wave: Represents depolarisation of atria before atrial contraction.

• QRS complex: Represents depolarisation of ventricles leading to ventricular contraction.

• T-wave: Represents repolarisation of ventricles after contraction.

• End of T-wave: Indicates completion of ventricular repolarisation and end of systole.

• Depolarisation: Change in membrane potential making it more positive, leading to contraction.

• Repolarisation: Restoration of resting membrane potential.

• Atria: Upper chambers of the heart receiving blood.

• Ventricles: Lower chambers of the heart pumping blood out.

• Systole: Phase of heart contraction.

• Diastole: Phase of heart relaxation.

Lead Question - 2023 (Manipur)

Match List - I with List - II

List-I (ECG)  List-II (Electrical activity of heart)

(A) P-wave — (I) Depolarisation of ventricles

(B) QRS complex — (II) End of systole

(C) T wave — (III) Depolarisation of atria

(D) End of T-wave — (IV) Repolarisation of ventricles

Choose the correct answer from the options given below:

Options: (A) (B) (C) (D)

1. IV I III II

2. I IV III II

3. IV III I II

4. III I IV II

Explanation:

In ECG interpretation, the P-wave represents depolarisation of atria before atrial contraction. The QRS complex reflects depolarisation of ventricles causing ventricular contraction. The T-wave indicates repolarisation of ventricles, and the end of T-wave corresponds to the end of systole. Matching these correctly: P-wave → III, QRS → I, T-wave → IV, End of T-wave → II. Hence, the correct option is 4. Understanding ECG waves is essential for assessing cardiac function, rhythm abnormalities, and diagnosing cardiovascular disorders. The sequence of electrical events ensures coordinated contraction of atria and ventricles.

1. Single Correct Answer MCQ:

Which ECG wave represents atrial depolarisation?

1. QRS complex

2. T-wave

3. P-wave

4. U-wave

Explanation:

The P-wave represents atrial depolarisation preceding atrial contraction. QRS complex is for ventricular depolarisation, T-wave for ventricular repolarisation, and U-wave is rarely observed. Hence, option 3 is correct.

2. Single Correct Answer MCQ:

QRS complex in ECG corresponds to:

1. Atrial depolarisation

2. Ventricular depolarisation

3. Ventricular repolarisation

4. End of systole

Explanation:

The QRS complex reflects ventricular depolarisation, which triggers ventricular contraction. Atrial depolarisation is P-wave, ventricular repolarisation is T-wave, and end of systole is marked by end of T-wave. Hence, option 2 is correct.

3. Single Correct Answer MCQ:

The T-wave in ECG indicates:

1. Ventricular depolarisation

2. Atrial depolarisation

3. Ventricular repolarisation

4. Start of systole

Explanation:

The T-wave represents repolarisation of ventricles after contraction. P-wave is atrial depolarisation, QRS is ventricular depolarisation, and start of systole is ventricular contraction. Hence, option 3 is correct.

4. Single Correct Answer MCQ:

End of T-wave corresponds to:

1. Start of systole

2. End of systole

3. Start of diastole

4. Atrial contraction

Explanation:

The end of T-wave marks the end of systole, indicating completion of ventricular repolarisation. Start of systole is QRS onset, start of diastole occurs after systole, and atrial contraction is during P-wave. Hence, option 2 is correct.

5. Single Correct Answer MCQ:

Which wave is absent during atrial repolarisation on standard ECG?

1. P-wave

2. QRS complex

3. T-wave

4. U-wave

Explanation:

Atrial repolarisation occurs during the QRS complex and is not visible separately on ECG because ventricular depolarisation dominates. P-wave is atrial depolarisation, T-wave is ventricular repolarisation, U-wave is sometimes seen. Hence, option 2 is correct.

6. Single Correct Answer MCQ:

Which ECG component indicates ventricular contraction?

1. P-wave

2. QRS complex

3. T-wave

4. End of T-wave

Explanation:

The QRS complex triggers ventricular depolarisation leading to contraction. P-wave is atrial depolarisation, T-wave is ventricular repolarisation, end of T-wave signals end of systole. Hence, option 2 is correct.

7. Assertion-Reason MCQ:

Assertion (A): QRS complex represents ventricular depolarisation.

Reason (R): It triggers ventricular contraction and ejects blood into arteries.

1. Both A and R are true and R explains A

2. Both A and R are true but R does not explain A

3. A is true but R is false

4. Both A and R are false

Explanation:

QRS complex indeed represents ventricular depolarisation, and this electrical activity causes ventricular contraction, ejecting blood into the aorta and pulmonary artery. Both statements are true, and R correctly explains A. Hence, option 1 is correct.

8. Matching Type MCQ:

Match the ECG component with its event:

A. P-wave — (i) Ventricular depolarisation

B. QRS — (ii) Atrial depolarisation

C. T-wave — (iii) Ventricular repolarisation

D. End of T — (iv) End of systole

1. A-(ii), B-(i), C-(iii), D-(iv)

2. A-(i), B-(ii), C-(iv), D-(iii)

3. A-(iii), B-(iv), C-(ii), D-(i)

4. A-(iv), B-(iii), C-(i), D-(ii)

Explanation:

P-wave → atrial depolarisation (ii), QRS → ventricular depolarisation (i), T-wave → ventricular repolarisation (iii), End of T → end of systole (iv). Correct matching is option 1.

9. Fill in the Blanks MCQ:

The ______ wave represents atrial depolarisation.

1. QRS

2. P

3. T

4. U

Explanation:

The P-wave corresponds to atrial depolarisation. QRS is for ventricular depolarisation, T-wave for ventricular repolarisation, and U-wave is rarely observed. Hence, option 2 is correct.

10. Choose the correct statements MCQ:

Statement I: T-wave represents ventricular repolarisation.

Statement II: P-wave represents ventricular contraction.

1. Statement I only

2. Statement II only

3. Both statements are true

4. Both statements are false

Explanation:

T-wave reflects ventricular repolarisation (Statement I correct). P-wave indicates atrial depolarisation, not ventricular contraction (Statement II false). Hence, only Statement I is correct, option 1.

Subtopic: White Blood Cells – Basophils and Immune Response

Keyword Definitions:
Basophils: Least abundant granulocytes in blood that secrete histamine, heparin, and serotonin during allergic and inflammatory reactions.
Histamine: A vasoactive compound causing dilation of blood vessels and increased permeability during inflammation.
Heparin: An anticoagulant preventing blood clot formation.
Serotonin: A neurotransmitter also aiding in inflammation regulation.
Inflammatory Response: Protective reaction of tissues against injury or infection involving immune cells and chemical mediators.
Agranulocytes: WBCs lacking granules in cytoplasm, including lymphocytes and monocytes.
Granulocytes: WBCs with granules in cytoplasm such as neutrophils, eosinophils, and basophils.
Leukocytes: White blood cells responsible for immune defense.
Neutrophils: Most abundant WBCs involved in phagocytosis of microbes.
Eosinophils: WBCs active in allergic responses and parasitic infections.

Lead Question (2023):
Which of the following statements are correct?
A. Basophils are most abundant cells of the total WBCs
B. Basophils secrete histamine, serotonin and heparin
C. Basophils are involved in inflammatory response
D. Basophils have kidney-shaped nucleus
E. Basophils are agranulocytes
Choose the correct answer from the options given below:
(1) B and C only
(2) A and B only
(3) D and E only
(4) C and E only

Answer & Explanation: Option (1) is correct. Basophils secrete histamine, serotonin, and heparin and participate in the inflammatory response. They are the least abundant granulocytes, not agranulocytes. Their lobed nucleus is often obscured by granules. By releasing vasoactive mediators, basophils help dilate blood vessels and recruit immune cells to infection sites, initiating protective inflammation.

1. Single Correct Answer MCQ: Which of the following white blood cells are least abundant in human blood?
A) Neutrophils
B) Eosinophils
C) Lymphocytes
D) Basophils

Answer & Explanation: Option D is correct. Basophils are the least abundant leukocytes, forming less than 1% of total WBCs. Despite their low number, they play an important role in allergic and inflammatory reactions by releasing histamine and other chemicals, which help regulate immune response and blood vessel dilation.

2. Single Correct Answer MCQ: The chemical heparin secreted by basophils acts as:
A) Anticoagulant
B) Coagulant
C) Neurotransmitter
D) Digestive enzyme

Answer & Explanation: Option A is correct. Heparin prevents blood clot formation by inhibiting thrombin activity. It helps maintain smooth blood flow during inflammation. Basophils release heparin alongside histamine and serotonin, ensuring that the site of injury remains supplied with immune cells for repair and defense.

3. Single Correct Answer MCQ: Which chemical mediator released by basophils causes vasodilation during inflammation?
A) Histamine
B) Heparin
C) Serotonin
D) Fibrin

Answer & Explanation: Option A is correct. Histamine causes vasodilation and increases capillary permeability during inflammation, enabling more immune cells to reach infected tissues. This process leads to redness and swelling characteristic of inflammation and aids in the immune system’s local defense mechanism.

4. Single Correct Answer MCQ: Which white blood cell type has granules containing histamine and heparin?
A) Neutrophils
B) Basophils
C) Monocytes
D) Lymphocytes

Answer & Explanation: Option B is correct. Basophils are granulocytes that store histamine and heparin in their cytoplasmic granules. These chemicals are released during immune responses to trigger vasodilation, anticoagulation, and recruitment of immune cells to inflamed areas, supporting tissue protection and healing.

5. Single Correct Answer MCQ: Which among the following WBCs are agranulocytes?
A) Lymphocytes and Monocytes
B) Neutrophils and Basophils
C) Basophils and Eosinophils
D) Eosinophils and Monocytes

Answer & Explanation: Option A is correct. Agranulocytes lack granules in their cytoplasm and include lymphocytes and monocytes. In contrast, neutrophils, eosinophils, and basophils are granulocytes. Agranulocytes are involved in immune memory, antibody formation, and phagocytosis of foreign particles.

6. Single Correct Answer MCQ: Which of the following statements about basophils is incorrect?
A) They are least numerous WBCs
B) They contain large granules
C) They have a kidney-shaped nucleus
D) They secrete histamine and heparin

Answer & Explanation: Option C is correct. Basophils do not have a kidney-shaped nucleus; it is bilobed and obscured by granules. Monocytes, not basophils, possess a kidney-shaped nucleus. Basophils secrete histamine and heparin and play vital roles in allergic and inflammatory processes.

7. Assertion-Reason MCQ:
Assertion (A): Basophils are involved in allergic and inflammatory responses.
Reason (R): They release histamine, heparin, and serotonin from their granules.
A) Both A and R are true, and R is the correct explanation of A
B) Both A and R are true, but R is not the correct explanation of A
C) A is true, but R is false
D) A is false, but R is true

Answer & Explanation: Option A is correct. Basophils mediate allergic and inflammatory responses by releasing vasoactive substances such as histamine, serotonin, and heparin. These chemicals enhance vascular permeability and attract other immune cells to infected or injured tissues, thus promoting immune defense and healing.

8. Matching Type MCQ:
Match the following WBCs with their main function:
A. Neutrophils - I. Phagocytosis of microbes
B. Eosinophils - II. Response to allergy and parasites
C. Basophils - III. Inflammatory and allergic reaction
D. Monocytes - IV. Transform into macrophages
Options:
1) A-I, B-II, C-III, D-IV
2) A-II, B-I, C-IV, D-III
3) A-IV, B-II, C-I, D-III
4) A-I, B-III, C-II, D-IV

Answer & Explanation: Option 1 is correct. Neutrophils are phagocytic, eosinophils respond to allergens and parasites, basophils mediate inflammatory reactions, and monocytes become macrophages. Together, they maintain body defense by performing distinct but cooperative immune functions.

9. Fill in the Blanks MCQ:
Basophils release _______ which acts as an anticoagulant, and _______ which causes vasodilation.
A) Heparin; Histamine
B) Serotonin; Fibrin
C) Histamine; Platelets
D) Heparin; Fibrin

Answer & Explanation: Option A is correct. Heparin acts as an anticoagulant preventing clot formation, while histamine promotes vasodilation, increasing blood flow and permeability during inflammation. These two molecules together support an efficient immune response.

10. Choose the Correct Statements MCQ:
Statement I: Basophils are granulocytes that release inflammatory mediators.
Statement II: Basophils are the most abundant WBCs in blood.
A) Both statements are correct
B) Both statements are incorrect
C) Only Statement I is correct
D) Only Statement II is correct

Answer & Explanation: Option C is correct. Basophils are granulocytes containing histamine and heparin-filled granules that mediate inflammation, but they are the least abundant among WBCs. Neutrophils are the most numerous. Thus, only Statement I is correct.

Topic: Cardiac Physiology; Subtopic: Electrocardiography (ECG) and Heart Conduction System

Keyword Definitions:
P-wave: Small upward deflection in ECG representing atrial depolarisation.
Q-wave: First negative deflection after P-wave, indicating septal depolarisation.
QRS complex: Series of waves representing ventricular depolarisation.
T-wave: Wave representing ventricular repolarisation.
Systole: Phase of heart contraction pumping blood out.
Depolarisation: Process where cardiac cells become electrically active.
Repolarisation: Return of cardiac cells to resting state.
ECG: Recording of electrical activity of the heart.
Electrocardiogram: Another term for ECG.
Atria: Upper heart chambers receiving blood.
Ventricles: Lower heart chambers pumping blood out.

Lead Question (2023): Match List I with List II
List I - List II
A. P-wave - I. Beginning of systole
B. Q-wave - II. Repolarisation of ventricles
C. QRS complex - III. Depolarisation of atria
D. T-wave - IV. Depolarisation of ventricles
Choose the correct answer from the options given below:

1) A-II, B-IV, C-I, D-III
2) A-I, B-II, C-III, D-IV
3) A-III, B-I, C-IV, D-II
4) A-IV, B-III, C-II, D-I

Answer & Explanation: Option 3 is correct. The P-wave corresponds to atrial depolarisation (A-III), the Q-wave represents the beginning of ventricular depolarisation (B-I), the QRS complex represents ventricular depolarisation (C-IV), and the T-wave represents ventricular repolarisation (D-II). This sequence accurately reflects the electrical events in a normal ECG, which is essential for diagnosing cardiac conditions. Understanding the correlation between ECG waves and cardiac events allows precise evaluation of heart function and detection of abnormalities, making it critical in cardiac physiology.

1. Single Correct Answer MCQ: The SA node initiates the heartbeat by generating impulses that spread across the atria. The correct statement about SA node is:
A) It is located in the interventricular septum
B) It is also called the pacemaker of the heart
C) It controls ventricular contraction directly
D) It produces the T-wave in ECG

Answer & Explanation: Option B is correct. The SA node is located in the right atrium and is known as the pacemaker because it initiates electrical impulses that cause atrial contraction. It does not directly control ventricular contraction but sets the rhythm. The impulses travel to AV node and His-Purkinje system. ECG records atrial and ventricular depolarisation and repolarisation, but T-wave is from ventricular repolarisation. Recognizing SA node function is fundamental for understanding cardiac physiology and ECG interpretation, especially for identifying arrhythmias.

2. Single Correct Answer MCQ: Which of the following waves in ECG represents ventricular depolarisation?
A) P-wave
B) QRS complex
C) T-wave
D) U-wave

Answer & Explanation: Option B is correct. The QRS complex reflects the rapid depolarisation of the ventricles, which triggers ventricular contraction. The P-wave represents atrial depolarisation, the T-wave represents ventricular repolarisation, and the U-wave is often absent but may indicate late ventricular repolarisation. Accurate identification of QRS is critical for diagnosing bundle branch blocks, arrhythmias, and myocardial infarction in ECG interpretation.

3. Single Correct Answer MCQ: The T-wave in ECG corresponds to:
A) Atrial depolarisation
B) Ventricular depolarisation
C) Ventricular repolarisation
D) SA node firing

Answer & Explanation: Option C is correct. The T-wave represents the repolarisation of the ventricles, returning the ventricular muscle cells to their resting state after contraction. Atrial repolarisation occurs but is masked within the QRS complex. Identifying the T-wave accurately is essential for evaluating electrolyte imbalances, ischemia, and myocardial infarction. Misinterpretation of T-wave changes may lead to incorrect clinical decisions.

4. Single Correct Answer MCQ: Which part of the conduction system delays the impulse to allow ventricular filling?
A) SA node
B) AV node
C) Bundle of His
D) Purkinje fibers

Answer & Explanation: Option B is correct. The AV node delays the electrical impulse from atria to ventricles, allowing complete ventricular filling before contraction. The SA node initiates the impulse, Bundle of His conducts impulses to ventricles, and Purkinje fibers rapidly distribute impulses. AV node delay is crucial for synchronised cardiac cycles, ensuring efficient blood flow and optimal cardiac output. Its dysfunction can cause heart block and bradyarrhythmias.

5. Single Correct Answer MCQ: Which ECG interval represents the time between atrial and ventricular depolarisation?
A) PR interval
B) QT interval
C) ST segment
D) RR interval

Answer & Explanation: Option A is correct. The PR interval measures the time from atrial depolarisation onset (P-wave) to ventricular depolarisation start (QRS complex), representing conduction through AV node, bundle of His, and Purkinje fibers. QT interval reflects ventricular depolarisation and repolarisation, ST segment indicates plateau phase, and RR interval measures heart rate. PR interval prolongation may indicate AV block.

6. Single Correct Answer MCQ: Which structure rapidly conducts impulses throughout the ventricles?
A) AV node
B) SA node
C) Purkinje fibers
D) Bundle of His

Answer & Explanation: Option C is correct. Purkinje fibers distribute impulses rapidly across ventricular myocardium, ensuring coordinated contraction. AV node delays impulse, SA node initiates it, and Bundle of His transmits impulses from AV node to ventricles. Purkinje fibers’ speed enables simultaneous ventricular contraction, optimizing blood ejection and cardiac efficiency. Dysfunction may lead to arrhythmias.

7. Assertion-Reason MCQ:
Assertion (A): The QRS complex masks atrial repolarisation.
Reason (R): Atrial repolarisation occurs simultaneously with ventricular depolarisation.
A) Both A and R are true and R is correct explanation of A
B) Both A and R are true but R is not correct explanation of A
C) A is true but R is false
D) A is false but R is true

Answer & Explanation: Option A is correct. The QRS complex represents ventricular depolarisation, which produces large electrical activity that obscures the smaller atrial repolarisation wave. Therefore, atrial repolarisation occurs during QRS but is not separately visible. Understanding this relationship is vital for interpreting ECGs accurately, diagnosing cardiac conditions, and distinguishing abnormal patterns in conduction and repolarisation.

8. Matching Type MCQ: Match the ECG components with their corresponding cardiac events:
List I - List II
A. P-wave - I. Ventricular repolarisation
B. QRS complex - II. Atrial depolarisation
C. T-wave - III. Ventricular depolarisation
Choose correct option:
1) A-II, B-III, C-I
2) A-III, B-I, C-II
3) A-I, B-II, C-III
4) A-II, B-I, C-III

Answer & Explanation: Option 1 is correct. P-wave indicates atrial depolarisation (A-II), QRS complex represents ventricular depolarisation (B-III), and T-wave corresponds to ventricular repolarisation (C-I). Matching ECG components with physiological events is essential to interpret cardiac cycles, detect arrhythmias, and identify myocardial infarction. Correct correlation allows accurate clinical assessment and monitoring of heart function.

9. Fill in the Blanks MCQ: The _______ interval represents the duration from the start of ventricular depolarisation to the end of repolarisation.
A) PR
B) QT
C) ST
D) RR

Answer & Explanation: Option B is correct. The QT interval measures the time from the beginning of ventricular depolarisation to the end of ventricular repolarisation. It reflects total ventricular electrical activity, and its prolongation or shortening indicates risks of arrhythmias. PR interval measures atrioventricular conduction, ST segment indicates plateau phase, and RR interval is for heart rate assessment. Monitoring QT interval is crucial in clinical cardiology.

10. Choose the Correct Statements MCQ:
Statement I: SA node initiates impulses that cause atrial contraction.
Statement II: T-wave represents atrial depolarisation.
A) Both statements are correct
B) Both statements are incorrect
C) Only Statement I is correct
D) Only Statement II is correct

Answer & Explanation: Option C is correct. SA node is the primary pacemaker initiating electrical impulses that result in atrial contraction. The T-wave does not represent atrial depolarisation; it represents ventricular repolarisation. Correct interpretation of these events is essential for accurate ECG analysis, detection of conduction abnormalities, and evaluation of cardiac rhythm disorders.

Chapter : Body Fluids and Circulation; Topic : Blood Composition; Subtopic : Formed Elements of Blood

Keyword Definitions :

• Erythrocytes : Red blood cells that transport oxygen and carbon dioxide.

• Leukocytes : White blood cells responsible for body defense mechanisms.

• Platelets : Small cell fragments involved in blood clotting.

• Neutrophils : The most abundant type of white blood cells that fight infections.

• Eosinophils : White blood cells that increase during allergic reactions and parasitic infections.

• Monocytes : Large phagocytic white blood cells that differentiate into macrophages.

Lead Question - 2022 (Ganganagar)
Arrange the following formed elements in the decreasing order of their abundance in blood in humans :
(a) Platelets
(b) Neutrophils
(c) Erythrocytes
(d) Eosinophils
(e) Monocytes
Choose the most appropriate answer from the options given below :
1. (c), (a), (b), (e), (d)
2. (c), (b), (a), (e), (d)
3. (d), (e), (b), (a), (c)
4. (a), (c), (b), (d), (e)

Explanation : The correct order of abundance is Erythrocytes (RBCs) > Neutrophils > Platelets > Monocytes > Eosinophils. Erythrocytes are the most abundant, making up about 5 million/mm³ of blood. Neutrophils form 60–65% of total WBCs, platelets are about 1.5–3 lakh/mm³, and monocytes and eosinophils are fewer. Hence, Option 2 is correct.

1. Which formed element of blood lacks a nucleus?
1. Neutrophil
2. Platelet
3. Monocyte
4. Lymphocyte

Explanation : Platelets, also known as thrombocytes, are small, anucleated cell fragments derived from megakaryocytes. They circulate in large numbers and play a vital role in blood clotting. Other blood cells, like leukocytes and erythrocytes (in mammals), have nuclei at some developmental stages. Thus, Option 2 is correct.

2. Which white blood cell is phagocytic and increases during chronic infections?
1. Basophil
2. Monocyte
3. Eosinophil
4. Lymphocyte

Explanation : Monocytes are large, phagocytic leukocytes that remove pathogens and dead cells from tissues. They differentiate into macrophages when they migrate into tissues and increase during chronic infections such as tuberculosis. Hence, Option 2 is correct.

3. Which of the following formed elements play an important role in blood clotting?
1. Platelets
2. RBCs
3. Lymphocytes
4. Neutrophils

Explanation : Platelets, or thrombocytes, release clotting factors such as thrombokinase that initiate the coagulation cascade, leading to fibrin clot formation. They prevent excessive blood loss after injury. RBCs and WBCs do not participate directly in coagulation. Therefore, Option 1 is correct.

4. Which of the following cells are agranulocytes?
1. Neutrophils and eosinophils
2. Basophils and monocytes
3. Lymphocytes and monocytes
4. Neutrophils and lymphocytes

Explanation : Agranulocytes lack visible cytoplasmic granules and include lymphocytes and monocytes. These cells play major roles in immunity and phagocytosis. Granulocytes include neutrophils, eosinophils, and basophils. Thus, Option 3 is correct.

5. Assertion (A): Erythrocytes have a biconcave shape.
Reason (R): The biconcave shape increases surface area for gas exchange.
1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, R is false
4. A is false, R is true

Explanation : Erythrocytes possess a biconcave shape that provides a large surface area for efficient diffusion of O₂ and CO₂ and allows flexibility in capillaries. Hence, both statements are true, and R correctly explains A. Therefore, Option 1 is correct.

6. Which type of WBC is responsible for allergic reactions?
1. Monocytes
2. Basophils
3. Eosinophils
4. Lymphocytes

Explanation : Eosinophils increase in number during allergic conditions and parasitic infections. They neutralize histamines and help regulate inflammatory responses. Their granules contain enzymes like peroxidase and acid phosphatase. Hence, Option 3 is correct.

7. (Matching Type)
Match List-I with List-II
List-I      List-II
(a) RBCs      (i) Blood clotting
(b) WBCs      (ii) Defense mechanism
(c) Platelets      (iii) Oxygen transport
1. (a)-(iii), (b)-(ii), (c)-(i)
2. (a)-(ii), (b)-(i), (c)-(iii)
3. (a)-(i), (b)-(iii), (c)-(ii)
4. (a)-(iii), (b)-(i), (c)-(ii)

Explanation : RBCs transport oxygen through hemoglobin, WBCs defend against pathogens, and platelets aid clotting. Their distinct roles maintain circulatory homeostasis. Thus, Option 1 is correct.

8. (Fill in the Blank)
_________ are the most abundant white blood cells in human blood.
1. Neutrophils
2. Lymphocytes
3. Monocytes
4. Eosinophils

Explanation : Neutrophils constitute about 60–65% of the total WBC count and form the first line of defense against infections. They phagocytose and destroy invading microorganisms. Hence, Option 1 is correct.

9. Which statement about platelets is incorrect?
1. They are derived from megakaryocytes.
2. They are nucleated.
3. They help in clot formation.
4. Their deficiency leads to delayed clotting.

Explanation : Platelets are non-nucleated cell fragments derived from megakaryocytes and aid clot formation. Their deficiency causes excessive bleeding (thrombocytopenia). Hence, Option 2 is incorrect.

10. (Choose the correct statements)
Statement I: Lymphocytes are responsible for antibody production.
Statement II: Neutrophils are involved in phagocytosis.
1. Both statements are correct
2. Only Statement I is correct
3. Only Statement II is correct
4. Both statements are incorrect

Explanation : Lymphocytes (especially B-lymphocytes) produce antibodies that mediate specific immune responses. Neutrophils engulf pathogens by phagocytosis and form the body’s primary defense. Hence, both statements are correct, making Option 1 correct.

Topic: Circulatory System; Subtopic: Heart Structure in Vertebrates

Keyword Definitions:
• Three-chambered heart: A heart with two atria and one ventricle, found in amphibians and most reptiles.
• Scoliodon: A genus of cartilaginous fish (sharks) with a two-chambered heart.
• Hippocampus: A genus of marine fish (seahorses) with two-chambered heart.
• Chelone: Turtles, reptiles having a three-chambered heart (except crocodilians).
• Pteropus: Bats, mammals with four-chambered heart.
• Heart Chambers: Compartments in the heart that receive and pump blood to maintain circulation.

Lead Question - 2022 (Ganganagar)

Which of the following animals has three chambered heart?
1. Scoliodon
2. Hippocampus
3. Chelone
4. Pteropus

Explanation: The correct answer is Chelone. Turtles, which belong to reptiles, have a three-chambered heart consisting of two atria and one ventricle. This allows partial mixing of oxygenated and deoxygenated blood, suitable for their ectothermic metabolism. Scoliodon and Hippocampus, being fish, have a two-chambered heart with one atrium and one ventricle. Pteropus, a mammal, has a four-chambered heart with complete separation of oxygenated and deoxygenated blood, unlike reptiles.

1. The number of atria in a three-chambered heart is:
1. One
2. Two
3. Three
4. Four

Explanation: The correct answer is two. A three-chambered heart has two atria and one ventricle. This arrangement allows separation of oxygenated and deoxygenated blood in atria, but the single ventricle causes partial mixing. It is characteristic of most reptiles and amphibians, providing adequate circulation for ectothermic metabolism.

2. Which animal has a four-chambered heart?
1. Frog
2. Chelone
3. Crocodile
4. Scoliodon

Explanation: The correct answer is crocodile. Crocodilians are unique among reptiles with a four-chambered heart, consisting of two atria and two ventricles, allowing complete separation of oxygenated and deoxygenated blood. Frogs and Chelone have three-chambered hearts, while Scoliodon (shark) has a two-chambered heart.

3. Which feature is common to all three-chambered hearts?
1. Two ventricles
2. Two atria and one ventricle
3. Complete separation of oxygenated and deoxygenated blood
4. Single atrium

Explanation: The correct answer is two atria and one ventricle. Three-chambered hearts are found in amphibians and most reptiles, allowing partial mixing of blood in the ventricle. Complete separation occurs only in four-chambered hearts of birds and mammals.

4. Scoliodon heart type is:
1. Three-chambered
2. Two-chambered
3. Four-chambered
4. Five-chambered

Explanation: The correct answer is two-chambered. Scoliodon, a shark, has one atrium and one ventricle. Blood flows in a single circuit from heart to gills to body and back. It is characteristic of fish, supporting their aquatic respiration and circulatory needs.

5. Which is a feature of mammalian hearts like Pteropus?
1. Single atrium
2. Single ventricle
3. Four chambers with complete separation
4. Two atria and one ventricle

Explanation: The correct answer is four chambers with complete separation. Mammals, including bats like Pteropus, have two atria and two ventricles, preventing mixing of oxygenated and deoxygenated blood. This supports high metabolic rates and endothermy.

6. Chelone belongs to which class?
1. Amphibia
2. Reptilia
3. Pisces
4. Mammalia

Explanation: The correct answer is Reptilia. Chelone represents turtles, reptiles with a three-chambered heart. Amphibians like frogs also have three-chambered hearts, but reptiles have more developed heart structure. Pisces (Scoliodon, Hippocampus) have two-chambered hearts, and mammals like Pteropus have four-chambered hearts.

7. Assertion-Reason Question:
Assertion (A): Reptiles like Chelone have a three-chambered heart.
Reason (R): This allows partial mixing of oxygenated and deoxygenated blood.

1. Both A and R correct and R explains A
2. Both A and R correct but R does not explain A
3. A correct, R incorrect
4. A incorrect, R correct

Explanation: The correct answer is option 1. Chelone, a turtle, has two atria and one ventricle. The single ventricle causes partial mixing of oxygen-rich and oxygen-poor blood. This arrangement meets metabolic requirements of ectothermic reptiles while conserving energy.

8. Matching Type:
Match the animal with heart type:
(a) Scoliodon - (i) Two-chambered
(b) Chelone - (ii) Three-chambered
(c) Pteropus - (iii) Four-chambered

1. (a)-(i), (b)-(ii), (c)-(iii)
2. (a)-(ii), (b)-(iii), (c)-(i)
3. (a)-(i), (b)-(iii), (c)-(ii)
4. (a)-(iii), (b)-(ii), (c)-(i)

Explanation: The correct answer is option 1. Scoliodon (shark) has a two-chambered heart, Chelone (turtle) has a three-chambered heart, and Pteropus (bat) has a four-chambered heart. This illustrates the evolution of heart complexity in vertebrates.

9. Fill in the Blanks:
The heart of amphibians and most reptiles has ______ atria and ______ ventricle.

1. Two, One
2. One, Two
3. Two, Two
4. One, One

Explanation: The correct answer is two, one. Amphibians and most reptiles like Chelone have two atria and one ventricle. This allows partial mixing of blood in the ventricle, which is sufficient for their ectothermic metabolism and oxygen requirements.

10. Choose the Correct Statements:
Statement I: Chelone has a three-chambered heart.
Statement II: Scoliodon has a four-chambered heart.

1. Only Statement I correct
2. Only Statement II correct
3. Both correct
4. Both incorrect

Explanation: The correct answer is option 1. Chelone, a reptile, has two atria and one ventricle (three-chambered heart). Scoliodon, a fish, has a two-chambered heart. Statement II is incorrect, making only Statement I correct.

Topic: Circulatory System; Subtopic: Heart Disorders

Keyword Definitions:

• Oxygen supply: The delivery of oxygen to tissues through blood circulation.

• Heart muscles: Myocardium, responsible for contraction and pumping of blood.

• Acute chest pain: Sudden pain in chest often due to reduced blood flow to heart muscles.

• Angina pectoris: Chest pain due to insufficient oxygen supply to heart muscles.

• Cardiac arrest: Sudden stoppage of heart activity leading to loss of circulation.

• Heart failure: Condition where heart cannot pump sufficient blood to meet body’s needs.

• Coronary Heart Disease: Disease caused by blockage or narrowing of coronary arteries.

• Myocardial ischemia: Condition of reduced blood flow to heart muscle.

• Circulatory system: Network of heart, blood, and vessels transporting nutrients and oxygen.

• Symptom: A sign or indication of a disease or disorder.

• Disorder: Abnormality in structure or function of an organ.

Lead Question - 2022 (Abroad)

Inadequate supply of oxygen to heart muscles leads to a symptom of acute chest pain. This disorder of the circulatory system is identified as:

1. Angina pectoris

2. Cardiac arrest

3. Heart failure

4. Coronary Heart Disease

Explanation: Angina pectoris is caused by insufficient oxygen delivery to heart muscles, leading to acute chest pain. Unlike cardiac arrest, heart failure, or coronary heart disease, angina is a symptom indicating myocardial ischemia. Prompt recognition and management prevent progression to severe heart conditions. Correct answer: 1

1. SINGLE CORRECT ANSWER MCQ

Which artery is primarily responsible for supplying blood to the myocardium?

1. Carotid artery

2. Coronary artery

3. Aorta

4. Pulmonary artery

Explanation: Coronary arteries branch from the aorta and provide oxygen-rich blood to the myocardium. Blockage of these arteries can cause ischemia and angina pectoris. Carotid supplies the brain, aorta distributes blood systemically, and pulmonary artery carries deoxygenated blood to lungs. Correct answer: 2

2. SINGLE CORRECT ANSWER MCQ

A prolonged blockage of coronary arteries may result in:

1. Angina pectoris

2. Myocardial infarction

3. Arrhythmia

4. Hypertension

Explanation: Prolonged coronary blockage prevents blood flow, causing permanent death of heart tissue, termed myocardial infarction. Angina is temporary ischemia, arrhythmia is irregular rhythm, and hypertension is high blood pressure. Correct answer: 2

3. SINGLE CORRECT ANSWER MCQ

Which of the following can trigger angina?

1. Physical exertion

2. Rest

3. Sleeping

4. Digestion of food

Explanation: Physical exertion increases oxygen demand of myocardium, which may exceed supply during coronary artery narrowing, triggering angina. Rest or sleep reduces demand, and digestion has minor effect unless combined with exertion. Correct answer: 1

4. SINGLE CORRECT ANSWER MCQ

Nitroglycerin relieves angina by:

1. Increasing heart rate

2. Dilating coronary vessels

3. Constricting blood vessels

4. Decreasing oxygen content of blood

Explanation: Nitroglycerin is a vasodilator that dilates coronary vessels, improving oxygen supply to ischemic myocardium, thus relieving angina. It does not increase heart rate, constrict vessels, or reduce oxygen content. Correct answer: 2

5. SINGLE CORRECT ANSWER MCQ

Which symptom is typical of angina pectoris?

1. Sudden unconsciousness

2. Severe chest pain on exertion

3. Persistent cough

4. Lower limb swelling

Explanation: Angina pectoris presents as severe, transient chest pain on exertion due to myocardial ischemia. Sudden unconsciousness may occur in cardiac arrest, cough is respiratory, swelling indicates heart failure. Correct answer: 2

6. SINGLE CORRECT ANSWER MCQ

Primary cause of angina is:

1. Myocardial hypertrophy

2. Coronary artery narrowing

3. Valve defect

4. Arrhythmia

Explanation: Angina occurs due to reduced blood supply from narrowed coronary arteries. Myocardial hypertrophy, valve defects, or arrhythmias may affect heart function but are not primary causes. Correct answer: 2

7. ASSERTION-REASON MCQ

Assertion (A): Angina pectoris is relieved by rest.

Reason (R): Rest reduces oxygen demand of myocardium.

1. Both A and R are true and R explains A

2. Both A and R are true but R does not explain A

3. A is true but R is false

4. A is false but R is true

Explanation: Rest lowers myocardial oxygen demand, alleviating chest pain in angina. Therefore, both assertion and reason are true, and reason explains assertion. Correct answer: 1

8. MATCHING TYPE MCQ

Match disorder with primary symptom:

Column A:

1. Angina pectoris

2. Cardiac arrest

3. Heart failure

4. Coronary heart disease

Column B:

1. Acute chest pain

2. Sudden stoppage of heart

3. Fluid retention

4. Artery blockage

Explanation: Angina presents as acute chest pain, cardiac arrest is sudden heart stoppage, heart failure shows fluid retention, and coronary heart disease involves arterial blockage. Matching ensures correct understanding of symptoms and pathophysiology. Correct matching: 1-1, 2-2, 3-3, 4-4

9. FILL IN THE BLANKS / COMPLETION MCQ

Chest pain due to inadequate oxygen supply to heart muscles is called ________.

1. Heart failure

2. Angina pectoris

3. Cardiac arrest

4. Arrhythmia

Explanation: Angina pectoris is the medical term for chest pain caused by reduced blood and oxygen supply to the myocardium. Other options refer to different heart conditions not characterized primarily by transient chest pain. Correct answer: 2

10. CHOOSE THE CORRECT STATEMENTS MCQ

Statement I: Angina is a symptom of myocardial ischemia.
Statement II: Coronary artery dilation can relieve angina.

1. Only Statement I is correct

2. Only Statement II is correct

3. Both Statements I and II are correct

4. Both Statements I and II are incorrect

Explanation: Angina is caused by myocardial ischemia. Vasodilators like nitroglycerin relieve angina by increasing oxygen supply. Therefore, both statements are correct and consistent with the pathophysiology. Correct answer: 3

Topic: Endocrine Regulation of Blood Pressure; Subtopic: Hormonal Control of Cardiovascular System

Keyword Definitions:

• Antidiuretic Hormone (ADH): Hormone secreted by posterior pituitary that increases water reabsorption in kidneys, raising blood pressure.

• Atrial Natriuretic Factor (ANF): Peptide hormone produced by atria of heart, promoting sodium and water excretion to reduce blood volume and pressure.

• Aldosterone: Mineralocorticoid hormone from adrenal cortex that increases sodium reabsorption in kidneys, indirectly increasing blood pressure.

• Angiotensin-II: Potent vasoconstrictor hormone that increases blood pressure by narrowing blood vessels and stimulating aldosterone secretion.

• Blood Pressure: Force exerted by circulating blood on walls of blood vessels, regulated by neural and hormonal mechanisms.

• Kidney: Organ responsible for maintaining fluid and electrolyte balance, and controlling blood pressure through renin-angiotensin-aldosterone system.

• Vasodilation: Widening of blood vessels to reduce vascular resistance and lower blood pressure.

• Hormonal Regulation: Control of physiological processes by hormones secreted by endocrine glands.

Lead Question - 2022 (Abroad)
Which one of the following hormones reduces the blood pressure?
1. Antidiuretic hormone
2. Atrial Natriuretic factor
3. Aldosterone
4. Angiotensin-II
Explanation: The correct answer is Atrial Natriuretic factor. ANF is released from the atrial walls of the heart in response to high blood volume or pressure. It promotes natriuresis, the excretion of sodium and water by kidneys, leading to decreased blood volume and vasodilation, which together reduce blood pressure. Unlike ADH, aldosterone, and angiotensin-II, which increase blood pressure through water retention or vasoconstriction, ANF serves as a counter-regulatory hormone, maintaining cardiovascular homeostasis. It is essential in preventing hypertension and maintaining proper fluid and electrolyte balance, acting directly on renal tubules and blood vessels to lower vascular resistance and circulating volume.

1. Single Correct Answer Type:
Which hormone promotes water retention and increases blood pressure?
1. Atrial Natriuretic factor
2. Antidiuretic hormone
3. Prolactin
4. Cortisol
Explanation: The correct answer is Antidiuretic hormone. ADH is secreted by the posterior pituitary in response to dehydration or low blood volume. It increases water reabsorption in renal collecting ducts, reducing urine output, and raising blood pressure. ANF, in contrast, decreases blood pressure. ADH does not directly influence sodium excretion like aldosterone, and prolactin and cortisol have different physiological functions. By maintaining blood volume, ADH is crucial for cardiovascular homeostasis, especially during fluid deficit or hemorrhage.

2. Single Correct Answer Type:
Which hormone directly causes vasodilation to reduce blood pressure?
1. Angiotensin-II
2. Atrial Natriuretic factor
3. Aldosterone
4. ADH
Explanation: The correct answer is Atrial Natriuretic factor. ANF binds to receptors on vascular smooth muscles and kidney cells, inducing vasodilation and promoting excretion of sodium and water. This combination lowers vascular resistance and blood volume, thereby decreasing blood pressure. Angiotensin-II and aldosterone increase pressure, and ADH primarily increases water reabsorption. ANF plays a crucial counter-regulatory role against hypertensive stimuli, maintaining homeostasis in the cardiovascular system and protecting organs from damage due to elevated blood pressure.

3. Single Correct Answer Type:
Aldosterone reduces blood pressure by:
1. Increasing sodium excretion
2. Increasing sodium retention
3. Promoting vasodilation
4. Inhibiting renin
Explanation: The correct answer is Increasing sodium retention. Aldosterone is a mineralocorticoid secreted from the adrenal cortex. It promotes sodium reabsorption in renal distal tubules and collecting ducts, leading to water retention and increased blood volume, which raises blood pressure. It does not reduce pressure or promote vasodilation. ANF, not aldosterone, reduces blood pressure. Aldosterone’s action is part of the renin-angiotensin-aldosterone system that regulates fluid balance and blood pressure, crucial for maintaining homeostasis in response to hypotension or low blood volume.

4. Single Correct Answer Type:
Angiotensin-II increases blood pressure primarily by:
1. Stimulating vasodilation
2. Stimulating aldosterone secretion and vasoconstriction
3. Inhibiting ADH
4. Increasing sodium excretion
Explanation: The correct answer is Stimulating aldosterone secretion and vasoconstriction. Angiotensin-II is a potent vasoconstrictor that narrows arterioles, increasing vascular resistance. It also stimulates aldosterone release from adrenal cortex, promoting sodium and water retention, which raises blood volume and pressure. This mechanism contrasts with ANF, which lowers blood pressure. Angiotensin-II is central to the renin-angiotensin-aldosterone system, regulating blood pressure and fluid balance in response to hypotension or dehydration, ensuring adequate perfusion to vital organs.

5. Single Correct Answer Type:
Which hormone’s release is triggered by increased atrial stretch due to high blood volume?
1. ADH
2. ANF
3. Aldosterone
4. Angiotensin-II
Explanation: The correct answer is ANF. Atrial Natriuretic Factor is secreted by atrial myocytes when they detect increased blood volume and pressure, causing atrial stretch. ANF promotes sodium and water excretion and vasodilation, effectively reducing blood pressure. ADH, aldosterone, and angiotensin-II have opposite effects, conserving water and increasing pressure. ANF acts as a counter-regulatory hormone to prevent hypertension, maintain fluid balance, and protect cardiovascular tissues, ensuring homeostasis in response to volume overload conditions.

6. Single Correct Answer Type:
Which hormone counteracts the effects of aldosterone?
1. ADH
2. Angiotensin-II
3. Atrial Natriuretic factor
4. Cortisol
Explanation: The correct answer is Atrial Natriuretic factor. ANF opposes aldosterone by promoting sodium and water excretion and vasodilation, reducing blood pressure. Aldosterone promotes sodium and water retention to raise pressure, while ANF decreases blood volume and vascular resistance. ADH and angiotensin-II enhance water retention and increase blood pressure. ANF maintains cardiovascular homeostasis, preventing hypertension and regulating fluid balance, acting as a physiological antagonist to the renin-angiotensin-aldosterone system.

7. Assertion-Reason Type:
Assertion (A): ANF lowers blood pressure.
Reason (R): ANF promotes sodium and water excretion and vasodilation.
1. Both A and R are correct, and R is the correct explanation of A
2. Both A and R are correct, but R is not the correct explanation of A
3. A is correct, R is false
4. A is false, R is true
Explanation: Correct answer is Both A and R are correct, and R is the correct explanation of A. ANF reduces blood pressure by promoting natriuresis and diuresis, decreasing blood volume. Additionally, it induces vasodilation, lowering vascular resistance. Together, these mechanisms counteract the effects of hormones like aldosterone and angiotensin-II, maintaining cardiovascular homeostasis. This regulation is critical for preventing hypertension, ensuring proper perfusion of organs, and protecting cardiac tissues from volume overload.

8. Matching Type:
Match the hormone with its primary effect on blood pressure:
A. ADH → (i) Decreases BP
B. ANF → (ii) Increases BP
C. Aldosterone → (iii) Increases BP via sodium retention
D. Angiotensin-II → (iv) Increases BP via vasoc

Topic: Circulatory System; Subtopic: Heart and Cardiac Function

Keyword Definitions:
- Tricuspid valve: Valve between right atrium and right ventricle.
- Bicuspid valve (Mitral valve): Valve between left atrium and left ventricle.
- Semilunar valves: Pulmonary and aortic valves controlling blood flow out of ventricles.
- Diastole: Relaxation phase of the heart chambers.
- Systole: Contraction phase of the heart chambers.
- Atria: Upper chambers of the heart receiving blood.
- Ventricles: Lower chambers pumping blood to lungs and body.
- Atrioventricular node (AVN): Node generating impulses for ventricular contraction.
- Action potential: Electrical signal initiating cardiac muscle contraction.
- Cardiac cycle: Sequence of atrial and ventricular contraction and relaxation.
- Blood circulation: Movement of blood through heart, lungs, and body.

Lead Question - 2022:
Which one of the following statements is correct?
(1) The tricuspid and the bicuspid valves open due to the pressure exerted by the simultaneous contraction of the atria
(2) Blood moves freely from atrium to the ventricle during joint diastole
(3) Increased ventricular pressure causes closing of the semilunar valves
(4) The atrio-ventricular node (AVN) generates an action potential to stimulate atrial contraction

Explanation: The correct answer is (3). Increased ventricular pressure during systole causes the semilunar valves to close, preventing backflow into atria. Tricuspid and bicuspid valves open due to atrial pressure, not simultaneous contraction. AVN stimulates ventricular, not atrial, contraction. Blood moves from atrium to ventricle mainly during atrial systole.

1. Single Correct Answer:
Which valve prevents backflow into the left ventricle?
(a) Tricuspid
(b) Bicuspid
(c) Aortic semilunar
(d) Pulmonary semilunar
Explanation: The aortic semilunar valve prevents backflow from the aorta into the left ventricle. Tricuspid and bicuspid valves prevent backflow into atria, and pulmonary semilunar valve prevents backflow from pulmonary artery into right ventricle.

2. Single Correct Answer:
Which chamber receives oxygenated blood from lungs?
(a) Right atrium
(b) Left atrium
(c) Right ventricle
(d) Left ventricle
Explanation: The left atrium receives oxygenated blood from the lungs via pulmonary veins. Right atrium receives deoxygenated blood, and ventricles pump blood to lungs and body.

3. Single Correct Answer:
During which phase do ventricles contract?
(a) Atrial diastole
(b) Ventricular systole
(c) Atrial systole
(d) Ventricular diastole
Explanation: Ventricular systole is the phase when ventricles contract to pump blood into the aorta and pulmonary artery. Atrial systole fills the ventricles, and diastole refers to relaxation phases of heart chambers.

4. Single Correct Answer:
Which node initiates the heartbeat?
(a) AVN
(b) SA node
(c) Purkinje fibers
(d) Bundle of His
Explanation: The SA node generates action potentials initiating the heartbeat, causing atrial contraction. AVN transmits impulses to ventricles, Purkinje fibers distribute signals, and Bundle of His conducts impulses but does not initiate them.

5. Single Correct Answer:
Which valves open due to atrial pressure?
(a) Semilunar valves
(b) Tricuspid and bicuspid valves
(c) Aortic valve
(d) Pulmonary valve
Explanation: Tricuspid and bicuspid valves open when atrial pressure exceeds ventricular pressure, allowing blood to flow into ventricles. Semilunar valves open when ventricular pressure exceeds arterial pressure to pump blood out.

6. Single Correct Answer:
Which fibers distribute impulses to ventricular myocardium?
(a) SA node fibers
(b) AVN fibers
(c) Purkinje fibers
(d) Bundle of His
Explanation: Purkinje fibers rapidly conduct action potentials throughout ventricles, ensuring coordinated contraction. SA node initiates heartbeat, AVN delays impulse, and Bundle of His conducts impulses from AVN to ventricles.

7. Assertion-Reason MCQ:
Assertion (A): Semilunar valves prevent backflow during ventricular relaxation.
Reason (R): Semilunar valves close when ventricular pressure falls below arterial pressure.
(a) Both A and R are true, R explains A
(b) Both A and R are true, R does not explain A
(c) A is true, R is false
(d) A is false, R is true
Explanation: Option (a) is correct. Semilunar valves close during ventricular diastole to prevent backflow. This occurs when ventricular pressure falls below arterial pressure. Both assertion and reason are true, and R directly explains A.

8. Matching Type MCQ:
Match cardiac components with their function:
List - I List - II
(a) SA node (i) Initiates heartbeat
(b) AV node (ii) Delays impulse
(c) Purkinje fibers (iii) Distributes impulse to ventricles
(d) Tricuspid valve (iv) Prevents backflow into atrium
Options:
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-i, c-iv, d-iii
(3) a-iii, b-iv, c-i, d-ii
(4) a-iv, b-iii, c-ii, d-i
Explanation: Option (1) is correct. SA node initiates heartbeat, AV node delays impulses, Purkinje fibers distribute impulses to ventricles, and tricuspid valve prevents backflow into right atrium, ensuring coordinated cardiac function.

9. Fill in the Blanks:
Blood moves from atrium to ventricle mainly during _______
(a) Ventricular systole
(b) Ventricular diastole
(c) Atrial systole
(d) Atrial diastole
Explanation: Blood moves from atrium to ventricle mainly during atrial systole. Ventricular contraction pumps blood into arteries. Ventricular diastole allows filling of ventricles, and atrial diastole corresponds to relaxation of atria.

10. Choose the Correct Statements:
Identify correct statements:
1. AV node delays impulses for ventricular filling.
2. Semilunar valves open during ventricular systole.
3. SA node initiates atrial and ventricular contraction simultaneously.

Topic: Blood and Circulation
Subtopic: Coagulation and Spleen Function

Keyword Definitions:
• Coagulum: A mass formed during blood clotting consisting of fibrin and trapped blood cells.
• Thrombin: Enzyme that converts fibrinogen into fibrin during coagulation.
• Fibrin: Insoluble protein threads forming the mesh in a blood clot.
• Spleen: Organ involved in filtration of blood, removal of old erythrocytes, and immune responses.
• Erythrocytes: Red blood cells responsible for oxygen transport.
• Platelets: Small cell fragments that aid in clot formation.
• Hemostasis: Process of stopping bleeding through vascular constriction, platelet plug, and clot formation.
• Clotting Factors: Plasma proteins involved in blood coagulation.
• Fibrinolysis: Process of clot breakdown after tissue repair.
• Reticuloendothelial System: Network including spleen that removes old blood cells and debris.

Lead Question (2022):
Given below are two statements:
Statement I: The coagulum is formed of network of threads called thrombins.
Statement II: Spleen is the graveyard of erythrocytes.
In the light of the above statements, choose the most appropriate answer from the options given below:
1. Both Statement I and Statement II are incorrect
2. Statement I is correct but Statement II is incorrect
3. Statement I is incorrect but Statement II is correct
4. Both Statement I and Statement II are correct

Explanation: The correct answer is 3. Statement I is incorrect because coagulum is formed of fibrin threads, not thrombins. Statement II is correct since the spleen removes aged and damaged erythrocytes from circulation, acting as the “graveyard” of red blood cells, and also contributes to immune surveillance.

Guessed MCQs:

1. Which enzyme converts fibrinogen to fibrin during coagulation?
Options:
(a) Thrombin
(b) Plasmin
(c) Prothrombin
(d) Heparin
Explanation: The correct answer is (a) Thrombin. Thrombin catalyzes the conversion of soluble fibrinogen into insoluble fibrin, forming the structural basis of a blood clot. Plasmin breaks clots, prothrombin is the inactive precursor of thrombin, and heparin is an anticoagulant.

2. Which cells primarily initiate platelet plug formation?
Options:
(a) Platelets
(b) Erythrocytes
(c) Leukocytes
(d) Endothelial cells
Explanation: The correct answer is (a) Platelets. Platelets adhere to damaged endothelium, release granules, and aggregate to form a temporary plug. Erythrocytes, leukocytes, and endothelial cells have supporting roles in coagulation and inflammation but do not initiate platelet plug formation.

3. Assertion-Reason MCQ:
Assertion (A): Fibrinolysis prevents excessive clot formation.
Reason (R): Plasminogen is converted to plasmin, which digests fibrin.
Options:
(a) Both A and R are true, R explains A
(b) Both A and R are true, R does not explain A
(c) A is true, R is false
(d) A is false, R is true
Explanation: The correct answer is (a). Fibrinolysis dissolves clots after tissue repair to prevent thrombosis. Plasminogen activation to plasmin digests fibrin, ensuring controlled clot removal and maintaining blood flow, explaining the physiological significance of fibrinolysis.

4. Matching Type MCQ:
Match the component with its function:
List - I List - II
(a) Spleen (i) Removes old erythrocytes
(b) Platelets (ii) Initiate clot formation
(c) Thrombin (iii) Converts fibrinogen to fibrin
Options:
1. a-i, b-ii, c-iii
2. a-ii, b-i, c-iii
3. a-i, b-iii, c-ii
4. a-iii, b-ii, c-i
Explanation: The correct answer is 1. The spleen removes aged red blood cells, platelets initiate the formation of a platelet plug, and thrombin converts fibrinogen into fibrin, forming the structural network of a coagulum, essential for hemostasis.

5. Which vitamin is essential for synthesis of clotting factors?
Options:
(a) Vitamin K
(b) Vitamin D
(c) Vitamin C
(d) Vitamin B12
Explanation: The correct answer is (a) Vitamin K. Vitamin K is required for γ-carboxylation of glutamate residues in clotting factors II, VII, IX, and X, essential for coagulation. Vitamin D regulates calcium metabolism, C aids collagen synthesis, and B12 supports erythropoiesis.

6. Single Correct Answer:
Which plasma protein is converted into fibrin during coagulation?
Options:
(a) Fibrinogen
(b) Albumin
(c) Globulin
(d) Hemoglobin
Explanation: The correct answer is (a) Fibrinogen. Fibrinogen is a soluble plasma protein converted to insoluble fibrin by thrombin during clot formation. Albumin maintains osmotic pressure, globulins are antibodies, and hemoglobin carries oxygen.

7. Fill in the Blanks:
The breakdown of blood clots after healing is called __________.
Options:
(a) Fibrinolysis
(b) Hemostasis
(c) Thrombosis
(d) Coagulation
Explanation: The correct answer is (a) Fibrinolysis. Fibrinolysis involves plasmin-mediated degradation of fibrin, removing clots after tissue repair. Hemostasis stops bleeding, thrombosis is pathological clot formation, and coagulation is clot formation.

8. Which organ stores platelets and filters blood?
Options:
(a) Spleen
(b) Liver
(c) Kidney
(d) Heart
Explanation: The correct answer is (a) Spleen. The spleen stores platelets, filters aged red cells, and participates in immune responses. Liver produces clotting factors, kidney filters plasma, and heart pumps blood but does not store platelets.

9. Single Correct Answer:
Which ion is required for multiple steps of coagulation cascade?
Options:
(a) Calcium
(b) Sodium
(c) Potassium
(d) Magnesium
Explanation: The correct answer is (a) Calcium. Calcium ions (Ca2+) act as cofactors for several coagulation enzymes, facilitating thrombin formation and fibrin stabilization. Sodium, potassium, and magnesium have other physiological roles but are not primary cofactors in coagulation.

10. Choose the correct statements:
(i) Fibrin forms the structural network of a clot
(ii) Spleen removes damaged erythrocytes
(iii) Thrombin forms the coagulum threads
(iv) Platelets initiate clot formation
Options:
(a) i, ii, iv
(b) i, iii, iv
(c) ii, iii, iv
(d) i, ii, iii, iv
Explanation: The correct answer is (a) i, ii, iv. Fibrin forms clot network, spleen removes old red blood cells, and platelets initiate clot formation. Thrombin converts fibrinogen to fibrin but does not form threads directly.

Subtopic: ABO Blood Group

• AB Blood Group: Blood group with both A and B antigens on RBC surface.

• Universal Recipient: Person who can receive blood from any ABO type due to absence of anti-A and anti-B antibodies in plasma.

• Antigens: Molecules on red blood cells recognized by the immune system.

• Antibodies: Proteins in plasma that react against foreign antigens.

• RBC (Red Blood Cells): Cells carrying oxygen and antigens on their surface.

• Plasma: Liquid component of blood containing antibodies, proteins, and nutrients.

• Blood transfusion: Transfer of blood or components from donor to recipient.

• Compatibility: Matching blood types to prevent agglutination during transfusion.

• A Blood Group: RBCs have A antigen and anti-B antibodies in plasma.

• B Blood Group: RBCs have B antigen and anti-A antibodies in plasma.

• O Blood Group: RBCs lack A and B antigens but plasma has both anti-A and anti-B antibodies.

Lead Question - 2021

Persons with 'AB' blood group are called as "Universal recipients". This is due to:

(1) Absence of antigens A and B in plasma
(2) Presence of antibodies, anti-A and anti-B, on RBCs
(3) Absence of antibodies, anti-A and anti-B, in plasma
(4) Absence of antigens A and B on the surface of RBCs

Explanation: Persons with AB blood group have both A and B antigens on RBCs but lack anti-A and anti-B antibodies in plasma. This absence of antibodies allows them to receive blood from any ABO group without immune reaction. Answer: Absence of antibodies, anti-A and anti-B, in plasma.

1. Single Correct Answer MCQ: Which blood group is called universal donor?
Options:
A. AB
B. O
C. A
D. B

Explanation: O blood group lacks A and B antigens on RBCs, preventing immune reactions in recipients. Therefore, O blood is universal donor. Answer: O.

2. Single Correct Answer MCQ: Which antibodies are present in plasma of B blood group?
Options:
A. Anti-A
B. Anti-B
C. Anti-A and Anti-B
D. None

Explanation: B blood group has B antigen on RBCs and anti-A antibodies in plasma to react against A antigens. Answer: Anti-A.

3. Single Correct Answer MCQ: Blood transfusion reaction occurs when:
Options:
A. Donor RBC antigens match recipient antibodies
B. Donor RBC antigens do not match recipient antibodies
C. Both donor and recipient are AB
D. Both donor and recipient are O

Explanation: Agglutination happens if donor RBC antigens are recognized by recipient antibodies, causing transfusion reaction. Answer: Donor RBC antigens match recipient antibodies.

4. Single Correct Answer MCQ: Plasma of O blood group contains:
Options:
A. No antibodies
B. Anti-A only
C. Anti-B only
D. Anti-A and Anti-B

Explanation: O blood group RBCs lack A and B antigens, so plasma has both anti-A and anti-B antibodies to prevent reaction against any donor antigens. Answer: Anti-A and Anti-B.

5. Single Correct Answer MCQ: Which antigen is present on RBCs of AB blood group?
Options:
A. A only
B. B only
C. Both A and B
D. None

Explanation: AB blood group has both A and B antigens on the surface of RBCs, allowing compatibility with any donor. Answer: Both A and B.

6. Single Correct Answer MCQ: Blood group lacking both antigens on RBCs is:
Options:
A. AB
B. O
C. A
D. B

Explanation: O blood group lacks A and B antigens, making it compatible with all recipients. Answer: O.

7. Assertion-Reason MCQ:
Assertion (A): AB blood group persons are universal recipients.
Reason (R): AB plasma contains anti-A and anti-B antibodies.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: AB persons are universal recipients because plasma lacks anti-A and anti-B antibodies. Reason given is false. Answer: A true, R false.

8. Matching Type MCQ:
Column I: 1. Universal donor 2. Universal recipient 3. Has anti-A 4. Has anti-B
Column II: A. O blood group B. AB blood group C. B blood group D. A blood group
Options:
A. 1-A, 2-B, 3-D, 4-C
B. 1-B, 2-A, 3-C, 4-D
C. 1-A, 2-B, 3-C, 4-D
D. 1-A, 2-B, 3-D, 4-B

Explanation: O blood group is universal donor, AB is universal recipient, B group has anti-A, A group has anti-B. Answer: 1-A, 2-B, 3-D, 4-C.

9. Fill in the Blank MCQ: The plasma of AB blood group has ______ antibodies.
Options:
A. Anti-A
B. Anti-B
C. Both anti-A and anti-B
D. None

Explanation: AB plasma lacks both anti-A and anti-B antibodies, allowing safe reception from all ABO groups. Answer: None.

10. Choose the correct statements MCQ:
(a) AB blood group has both A and B antigens.
(b) AB blood group lacks anti-A and anti-B antibodies.
(c) O blood group is universal recipient.
(d) O blood group lacks antigens A and B.
Options:
1. (a), (b), (d) only
2. (a) and (b) only
3. (b) and (c) only
4. All of the above

Explanation: AB group has both antigens and no antibodies; O group lacks antigens and is universal donor, not recipient. Correct statements: (a), (b), (d). Answer: (a), (b), (d) only.

Subtopic: Coagulation and Hemostasis

• Fibrinogen: Soluble plasma protein produced by liver, converted to fibrin during blood clotting.

• Fibrin: Insoluble protein threads forming the mesh of a blood clot.

• Thrombin: Enzyme that catalyzes conversion of fibrinogen to fibrin in the coagulation cascade.

• Renin: Kidney enzyme regulating blood pressure, not involved in clotting.

• Epinephrine: Hormone involved in fight-or-flight response, not in coagulation.

• Thrombokinase: Also called tissue factor, activates clotting cascade to generate thrombin.

• Coagulation: Process of blood clot formation to prevent bleeding.

• Platelets: Blood cells that initiate clot formation by releasing clotting factors.

• Hemostasis: Sequence of events to stop bleeding: vasoconstriction, platelet plug, coagulation.

• Clotting factors: Proteins in plasma that act sequentially to form a fibrin clot.

• Prothrombin: Plasma protein converted to thrombin by clotting factors during coagulation.

Lead Question - 2021

Which enzyme is responsible for the conversion of inactive fibrinogens to fibrins?

(1) Renin
(2) Epinephrine
(3) Thrombokinase
(4) Thrombin

Explanation: Thrombin is the enzyme that converts soluble fibrinogen into insoluble fibrin during blood coagulation. Thrombokinase (tissue factor) activates prothrombin to thrombin. Renin regulates blood pressure and epinephrine is a hormone. The clot is formed by a fibrin mesh, stabilizing hemostasis. Answer: Thrombin.

1. Single Correct Answer MCQ: Which plasma protein is converted to fibrin by thrombin?
Options:
A. Albumin
B. Fibrinogen
C. Globulin
D. Prothrombin

Explanation: Fibrinogen is a soluble plasma protein that thrombin converts into insoluble fibrin, forming the structural basis of a blood clot. Prothrombin is converted to thrombin. Answer: Fibrinogen.

2. Single Correct Answer MCQ: Thrombokinase mainly functions to:
Options:
A. Convert fibrinogen to fibrin
B. Activate prothrombin to thrombin
C. Break down clots
D. Regulate blood pressure

Explanation: Thrombokinase, also called tissue factor, initiates the clotting cascade by activating prothrombin to thrombin. Thrombin then converts fibrinogen to fibrin. Answer: Activate prothrombin to thrombin.

3. Single Correct Answer MCQ: Which factor directly forms the fibrin mesh in clotting?
Options:
A. Prothrombin
B. Thrombin
C. Fibrinogen
D. Platelets

Explanation: Thrombin acts on fibrinogen to produce insoluble fibrin strands, forming the fibrin mesh that stabilizes blood clots. Platelets provide a surface for clotting but do not form fibrin. Answer: Thrombin.

4. Single Correct Answer MCQ: Which organ produces fibrinogen?
Options:
A. Kidney
B. Liver
C. Spleen
D. Bone marrow

Explanation: Liver synthesizes fibrinogen, a soluble plasma protein required for coagulation. Deficiency impairs clot formation. Other organs do not produce fibrinogen. Answer: Liver.

5. Single Correct Answer MCQ: Which enzyme is not involved in coagulation?
Options:
A. Thrombin
B. Thrombokinase
C. Renin
D. Factor X

Explanation: Renin regulates blood pressure and the renin-angiotensin system, not coagulation. Thrombin, thrombokinase, and Factor X are part of the clotting cascade. Answer: Renin.

6. Single Correct Answer MCQ: Thrombin converts fibrinogen into:
Options:
A. Prothrombin
B. Fibrin
C. Plasmin
D. Collagen

Explanation: Thrombin catalyzes the conversion of soluble fibrinogen into insoluble fibrin, which forms the mesh stabilizing blood clots. Answer: Fibrin.

7. Assertion-Reason MCQ:
Assertion (A): Thrombin is essential for blood coagulation.
Reason (R): It converts fibrinogen to fibrin forming the clot matrix.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: Thrombin is essential as it converts fibrinogen into insoluble fibrin, forming the clot. This explains its key role in hemostasis. Both assertion and reason are correct, with reason explaining the assertion. Answer: Both A and R true, R correct explanation.

8. Matching Type MCQ:
Column I: 1. Fibrinogen 2. Prothrombin 3. Thrombokinase 4. Thrombin
Column II: A. Activated by tissue factor B. Converted to fibrin C. Soluble plasma protein D. Enzyme converting fibrinogen
Options:
A. 1-C, 2-A, 3-D, 4-B
B. 1-C, 2-A, 3-A, 4-D
C. 1-B, 2-C, 3-A, 4-D
D. 1-C, 2-D, 3-A, 4-B

Explanation: Fibrinogen is soluble plasma protein, prothrombin is activated by thrombokinase, thrombin converts fibrinogen to fibrin. Correct matching: 1-C, 2-A, 3-A, 4-D. Answer: 1-C, 2-A, 3-A, 4-D.

9. Fill in the Blank MCQ: _______ converts fibrinogen into insoluble fibrin during coagulation.
Options:
A. Renin
B. Thrombin
C. Epinephrine
D. Thrombokinase

Explanation: Thrombin is the enzyme responsible for converting soluble fibrinogen into insoluble fibrin threads that form the structural clot. Answer: Thrombin.

10. Choose the correct statements MCQ:
(a) Thrombin converts fibrinogen to fibrin.
(b) Thrombokinase activates prothrombin.
(c) Renin converts fibrinogen to fibrin.
(d) Fibrin forms the clot matrix.
Options:
1. (a), (b), (d) only
2. (a), (c), (d) only
3. (b) and (c) only
4. All of the above

Explanation: Thrombin converts fibrinogen to fibrin, thrombokinase activates prothrom

Subtopic: Hormonal Regulation of Blood Cells

• Erythropoietin (EPO): Hormone that stimulates red blood cell production in the bone marrow.

• Juxtaglomerular Cells: Specialized kidney cells that detect blood oxygen levels and secrete erythropoietin.

• Rostral Adenohypophysis: Anterior pituitary lobe that secretes various hormones, not EPO.

• Alpha Cells: Pancreatic cells that secrete glucagon, not EPO.

• Bone Marrow: Site of hematopoiesis where erythrocytes are produced.

• RBC Formation: Production of red blood cells stimulated by erythropoietin.

• Hypoxia: Low oxygen levels in tissues triggering erythropoietin release.

• Endocrine Hormones: Chemical messengers secreted by glands into blood to regulate body functions.

• Feedback Regulation: Mechanism controlling hormone release based on physiological need.

• Hematopoietic Stem Cells: Precursor cells in bone marrow giving rise to blood cells.

• Kidney Function: Erythropoietin secretion is part of kidney response to hypoxia.

Lead Question - 2021

Erythropoietin hormone which stimulates R.B.C. formation is produced by :

Options:
1. The cells of rostral adenohypophysis
2. The cells of bone marrow
3. Juxtaglomerular cells of the kidney
4. Alpha cells of pancreas

Explanation: Erythropoietin is secreted by juxtaglomerular cells of the kidney in response to hypoxia. It stimulates the bone marrow to produce red blood cells, ensuring oxygen transport in the body. Pituitary and pancreatic cells do not secrete this hormone. Answer: Juxtaglomerular cells of the kidney.

1. Which condition triggers erythropoietin secretion?
Options:
A. High oxygen levels
B. Low oxygen levels (hypoxia)
C. High glucose
D. Low calcium

Explanation: Hypoxia or low oxygen concentration stimulates juxtaglomerular cells to secrete erythropoietin, enhancing RBC production to improve oxygen delivery. High oxygen or unrelated signals like glucose do not trigger EPO. Answer: Low oxygen levels (hypoxia).

2. What is the main site of RBC production stimulated by erythropoietin?
Options:
A. Kidney
B. Liver
C. Bone marrow
D. Spleen

Explanation: Bone marrow contains hematopoietic stem cells that differentiate into erythrocytes. Erythropoietin secreted by kidney cells acts on these stem cells to increase RBC production. The kidney produces the hormone, not the cells directly. Answer: Bone marrow.

3. Which organ does not produce erythropoietin?
Options:
A. Kidney
B. Liver (adult)
C. Rostral adenohypophysis
D. Juxtaglomerular cells

Explanation: In adults, the kidney juxtaglomerular cells secrete erythropoietin. The rostral adenohypophysis (anterior pituitary) does not produce EPO. The fetal liver can produce some EPO, but in adults, liver contribution is minimal. Answer: Rostral adenohypophysis.

4. Erythropoietin primarily acts on:
Options:
A. Alpha cells of pancreas
B. Hematopoietic stem cells in bone marrow
C. Kidney tubules
D. Liver hepatocytes

Explanation: Erythropoietin targets hematopoietic stem cells in the bone marrow to stimulate proliferation and differentiation into red blood cells, thereby increasing oxygen-carrying capacity. Other organs are not the primary targets. Answer: Hematopoietic stem cells in bone marrow.

5. Which pancreatic cells are unrelated to erythropoietin?
Options:
A. Beta cells
B. Alpha cells
C. Delta cells
D. All of the above

Explanation: Pancreatic cells, including alpha, beta, and delta cells, secrete hormones like glucagon, insulin, and somatostatin. They are unrelated to erythropoietin secretion. Kidney juxtaglomerular cells produce EPO, not pancreatic cells. Answer: All of the above.

6. Which of these hormones regulates RBC production?
Options:
A. Insulin
B. Erythropoietin
C. Cortisol
D. Thyroxine

Explanation: Erythropoietin specifically regulates red blood cell formation by acting on bone marrow hematopoietic stem cells. Other hormones regulate metabolism, stress, or growth. Answer: Erythropoietin.

7. Assertion-Reason:
Assertion (A): Kidney secretes erythropoietin in response to hypoxia.
Reason (R): Low oxygen stimulates juxtaglomerular cells to produce EPO.
Options:
A. Both A and R are true, R is correct explanation
B. Both A and R are true, R is not correct explanation
C. A is true, R is false
D. A is false, R is true

Explanation: The kidney detects hypoxia and juxtaglomerular cells respond by secreting erythropoietin to stimulate RBC formation in bone marrow. The reason accurately explains the assertion. Answer: Both A and R are true, R is correct explanation.

8. Match the following:
Column I: 1. Erythropoietin 2. Alpha cells 3. Beta cells 4. Delta cells
Column II: A. Secretes insulin B. Secretes glucagon C. Stimulates RBC production D. Secretes somatostatin
Options:
A. 1-C, 2-B, 3-A, 4-D
B. 1-B, 2-C, 3-D, 4-A
C. 1-A, 2-B, 3-C, 4-D
D. 1-D, 2-A, 3-B, 4-C

Explanation: Correct matching: Erythropoietin – RBC production (C), Alpha cells – Glucagon (B), Beta cells – Insulin (A), Delta cells – Somatostatin (D). Answer: 1-C, 2-B, 3-A, 4-D.

Subtopic: Regulation of Heart Rate and Cardiac Output

Keyword Definitions:
Cardiac Output: The volume of blood pumped by the heart per minute, product of heart rate and stroke volume.
Sympathetic nerves: Part of autonomic nervous system, increases heart rate and cardiac output.
Parasympathetic neural signals: Autonomic nerves that decrease heart rate and cardiac output.
Pneumotaxic center: Brainstem region controlling breathing pattern, not directly cardiac output.
Adrenal medullary hormones: Epinephrine and norepinephrine released from adrenal medulla, increase heart rate and cardiac output.
Stroke Volume: Amount of blood ejected by the ventricle per beat.
Autonomic Nervous System: Regulates involuntary body functions including heart rate and blood pressure.
Heart Rate: Number of heartbeats per minute.

Lead Question - 2020 (COVID Reexam):
Which of the following is associated with a decrease in cardiac output?
1. Sympathetic nerves
2. Parasympathetic neural signals
3. Pneumotaxic center
4. Adrenal medullary hormones
Explanation: Parasympathetic neural signals reduce heart rate and stroke volume, resulting in decreased cardiac output. Sympathetic nerves and adrenal medullary hormones increase heart rate and cardiac output. The pneumotaxic center regulates breathing and has no direct effect on cardiac output. Correct answer is 2. Parasympathetic neural signals.

1. Single Correct Answer MCQ:
Which nervous system increases cardiac output?
1. Parasympathetic
2. Sympathetic
3. Enteric
4. Somatic
Explanation: Sympathetic nerves increase heart rate and stroke volume, elevating cardiac output. Parasympathetic decreases it, enteric regulates gut, and somatic controls voluntary muscles. Correct answer is 2. Sympathetic.

2. Single Correct Answer MCQ:
Which hormone increases heart rate and cardiac output?
1. Epinephrine
2. Acetylcholine
3. GABA
4. Dopamine
Explanation: Epinephrine, secreted by adrenal medulla, stimulates the heart to increase rate and cardiac output. Acetylcholine reduces heart rate via parasympathetic nerves. GABA and dopamine are primarily neurotransmitters with no direct cardiac output effect. Correct answer is 1. Epinephrine.

3. Single Correct Answer MCQ:
Which part of the nervous system decreases heart rate?
1. Sympathetic
2. Parasympathetic
3. Somatic
4. Enteric
Explanation: Parasympathetic nervous system slows the heart by releasing acetylcholine, decreasing cardiac output. Sympathetic increases heart rate, somatic controls voluntary muscles, and enteric regulates gut. Correct answer is 2. Parasympathetic.

4. Single Correct Answer MCQ:
Stroke volume is reduced by:
1. Sympathetic stimulation
2. Parasympathetic stimulation
3. Adrenaline
4. Thyroid hormones
Explanation: Parasympathetic stimulation reduces stroke volume by decreasing ventricular contraction strength, lowering cardiac output. Sympathetic nerves, adrenaline, and thyroid hormones enhance contraction and increase output. Correct answer is 2. Parasympathetic stimulation.

5. Single Correct Answer MCQ:
Which factor has no direct effect on cardiac output?
1. Sympathetic nerves
2. Pneumotaxic center
3. Adrenal medulla hormones
4. Parasympathetic nerves
Explanation: Pneumotaxic center regulates breathing patterns, not heart rate or stroke volume, so it does not directly affect cardiac output. Sympathetic, parasympathetic, and adrenal hormones directly influence cardiac output. Correct answer is 2. Pneumotaxic center.

6. Single Correct Answer MCQ:
Which neurotransmitter decreases cardiac output?
1. Acetylcholine
2. Norepinephrine
3. Epinephrine
4. Dopamine
Explanation: Acetylcholine is released by parasympathetic nerves and decreases heart rate, lowering cardiac output. Norepinephrine and epinephrine increase heart rate, and dopamine has limited cardiac effect. Correct answer is 1. Acetylcholine.

7. Assertion-Reason MCQ:
Assertion (A): Parasympathetic stimulation decreases cardiac output.
Reason (R): It slows heart rate and reduces stroke volume.
1. Both A and R are true, R is correct explanation of A
2. Both A and R are true, R is not correct explanation of A
3. A is true, R is false
4. A is false, R is true
Explanation: Parasympathetic stimulation reduces heart rate and stroke volume, resulting in decreased cardiac output. Both statements are true, and the reason correctly explains the assertion. Correct answer is 1. Both A and R are true, R is correct explanation.

8. Matching Type MCQ:
Match the factor with its effect on cardiac output:
A. Sympathetic nerves B. Parasympathetic nerves C. Adrenal medulla hormones D. Pneumotaxic center
1. Increase CO
2. Decrease CO
3. Increase CO
4. No direct effect
Options:
1. A-1, B-2, C-3, D-4
2. A-2, B-1, C-3, D-4
3. A-1, B-3, C-2, D-4
4. A-2, B-3, C-1, D-4
Explanation: Sympathetic nerves increase cardiac output (A-1), parasympathetic nerves decrease it (B-2), adrenal medulla hormones increase it (C-3), and pneumotaxic center has no direct effect (D-4). Correct answer is 1. A-1, B-2, C-3, D-4.

9. Fill in the Blanks MCQ:
________ stimulation slows heart rate and reduces cardiac output.
1. Sympathetic
2. Parasympathetic
3. Adrenaline
4. Thyroid
Explanation: Parasympathetic stimulation releases acetylcholine, slowing the heart and reducing stroke volume, thereby lowering cardiac output. Sympathetic and adrenal hormones increase heart rate. Thyroid affects metabolism. Correct answer is 2. Parasympathetic.

10. Choose the correct statements MCQ:
Select correct statements about cardiac output regulation:
1. Sympathetic stimulation increases cardiac output
2. Parasympathetic stimulation decreases cardiac output
3. Pneumotaxic center directly increases cardiac output
4. Adrenal medulla hormones increase cardiac output
Options:
1. 1, 2, 4
2. 1 and 3
3. 2 and 3
4. 3 and 4
Explanation: Sympathetic nerves and adrenal medulla hormones increase cardiac output (1 and 4). Parasympathetic stimulation decreases it (2). Pneumotaxic center regulates breathing and does not directly affect cardiac output. Correct statements are 1, 2, 4. Correct answer is 1. 1, 2, 4.

Subtopic: Rh Incompatibility and Erythroblastosis Fetalis

Keyword Definitions:

• Rh factor: An antigen present on the surface of red blood cells, either Rh positive or negative.

• Erythroblastosis fetalis: Hemolytic disease of the newborn caused by Rh incompatibility between mother and fetus.

• Hemolysis: Breakdown of red blood cells, releasing hemoglobin into the blood.

• Antibodies: Proteins produced by the immune system to neutralize foreign antigens.

• Placenta: Organ connecting mother and fetus for nutrient and gas exchange.

Lead Question - 2020 (COVID Reexam)
Which of the following conditions causes erythroblastosis fetalis?

1. Mother Rh+ve and fetus Rh-ve
2. Mother Rh-ve and fetus Rh+ve
3. Both mother and fetus Rh-ve
4. Both mother and fetus Rh+ve

Explanation: Erythroblastosis fetalis occurs when an Rh-negative mother carries an Rh-positive fetus. Fetal blood entering maternal circulation stimulates antibody production against Rh antigen. In subsequent pregnancies, these maternal antibodies cross the placenta, causing hemolysis of fetal red blood cells. Correct answer is option 2, mother Rh-ve and fetus Rh+ve.

1. In Rh incompatibility, antibodies are produced in __________?

a) Fetus
b) Mother
c) Both fetus and mother
d) Placenta

Explanation: Rh incompatibility results when fetal blood enters maternal circulation. The Rh-negative mother recognizes Rh-positive cells as foreign, producing IgG antibodies. These cross the placenta during future pregnancies and cause hemolysis. Thus, antibodies are formed in the mother. Correct answer is option b.

2. Which immunoglobulin causes hemolysis in erythroblastosis fetalis?

a) IgA
b) IgM
c) IgG
d) IgE

Explanation: IgG is the only immunoglobulin that readily crosses the placenta. In Rh incompatibility, maternal IgG antibodies attack fetal red blood cells, causing hemolysis. IgM is too large to cross the placenta. Therefore, IgG is responsible. Correct answer is option c.

3. Which condition prevents erythroblastosis fetalis?

a) Rh-ve mother and Rh+ve fetus
b) Rh+ve mother and Rh-ve fetus
c) Both Rh+ve
d) Both Rh-ve

Explanation: Erythroblastosis fetalis occurs only if the mother is Rh-negative and the fetus is Rh-positive. If both are Rh negative or both Rh positive, no incompatibility develops. Correct answer is option d, both Rh-ve.

4. Clinical feature of erythroblastosis fetalis is:

a) Jaundice
b) Edema
c) Anemia
d) All of the above

Explanation: Hemolysis in the fetus leads to anemia. Excess bilirubin causes jaundice. Severe cases cause edema, termed hydrops fetalis. Therefore, anemia, jaundice, and edema all appear. Correct answer is option d.

5. Which drug prevents erythroblastosis fetalis?

a) Rh immunoglobulin (RhoGAM)
b) Anti-IgG
c) Anti-IgM
d) Anti-IgE

Explanation: Rh immunoglobulin (RhoGAM) neutralizes fetal Rh-positive cells in maternal circulation, preventing antibody formation. This prophylaxis is given to Rh-negative mothers after delivery or miscarriage. Correct answer is option a.

6. Which pregnancy is most affected by erythroblastosis fetalis?

a) First
b) Second or subsequent
c) Only twins
d) Never occurs

Explanation: During the first Rh-incompatible pregnancy, maternal sensitization occurs, usually without severe fetal impact. In subsequent pregnancies, maternal IgG antibodies cause severe hemolysis in the fetus. Thus, second or later pregnancies are most affected. Correct answer is option b.

7. Assertion (A): Erythroblastosis fetalis occurs due to Rh incompatibility.
Reason (R): Rh-positive mother forms antibodies against Rh-negative fetal cells.

a) Both A and R true, R correct explanation
b) Both A and R true, R not correct explanation
c) A true, R false
d) A false, R true

Explanation: Erythroblastosis fetalis occurs due to maternal sensitization when Rh-negative mother carries Rh-positive fetus. The given reason states Rh-positive mother makes antibodies against Rh-negative fetus, which is false. Correct answer is option c.

8. Match the following:

A. Rh antigen — i) Placenta
B. IgG — ii) Crosses placenta
C. Hemolysis — iii) Red blood cells
D. Nutrient exchange — iv) Antigen protein

a) A-iv, B-ii, C-iii, D-i
b) A-i, B-iv, C-ii, D-iii
c) A-iii, B-i, C-iv, D-ii
d) A-ii, B-iii, C-iv, D-i

Explanation: Rh antigen is a protein antigen, IgG crosses placenta, hemolysis involves red blood cells, and nutrient exchange occurs through placenta. Correct answer is option a.

9. Fill in the blank: Administration of __________ to Rh-negative mothers prevents erythroblastosis fetalis.

a) Rh immunoglobulin
b) Plasma
c) IgM
d) Bilirubin

Explanation: Giving Rh immunoglobulin (RhoGAM) neutralizes Rh-positive fetal cells before the mother produces antibodies. This prevents maternal sensitization and erythroblastosis fetalis. Correct answer is option a.

10. Choose the correct statements:
1. Erythroblastosis fetalis is caused by ABO incompatibility.
2. RhoGAM prevents Rh antibody formation.
3. IgM crosses placenta and destroys fetal cells.
4. Rh incompatibility develops when mother Rh-ve, fetus Rh+ve.

a) 1 and 3
b) 2 and 4
c) 1, 2 and 3
d) 2, 3 and 4

Explanation: Erythroblastosis fetalis is not due to ABO incompatibility. RhoGAM prevents maternal sensitization. IgM cannot cross placenta. Rh incompatibility occurs if mother is Rh negative and fetus Rh positive. Correct statements are 2 and 4. Correct answer is option b.

Topic: Cardiovascular System

Subtopic: Electrocardiography (ECG)

Keyword Definitions:

• ECG (Electrocardiogram) – A recording of the electrical activity of the heart over time.

• QRS complex – Represents depolarisation of ventricles leading to ventricular contraction.

• P wave – Depolarisation of atria (auricles) before contraction.

• T wave – Repolarisation of ventricles after contraction.

• Depolarisation – Process where cardiac muscle cells lose polarity, causing contraction.

• Repolarisation – Restoration of resting membrane potential after contraction.

Lead Question - 2020

The QRS complex in a standard ECG represents:

(1) Depolarisation of ventricles
(2) Repolarisation of ventricles
(3) Repolarisation of auricles
(4) Depolarisation of auricles

Explanation: The QRS complex represents rapid depolarisation of the ventricles, leading to ventricular contraction. The atrial depolarisation is masked by the large ventricular signal. Repolarisation of ventricles occurs later, forming the T wave. Correct answer is (1) Depolarisation of ventricles.

1. Which ECG wave represents atrial depolarisation?
(1) P wave
(2) QRS complex
(3) T wave
(4) U wave

Explanation: The P wave reflects depolarisation of atria (auricles) preceding their contraction. It is the first small upward deflection in a standard ECG. Correct answer is (1) P wave.

2. Repolarisation of ventricles is indicated by which ECG wave?
(1) P wave
(2) QRS complex
(3) T wave
(4) U wave

Explanation: The T wave represents ventricular repolarisation, returning the cells to resting potential after contraction. It follows the QRS complex. Correct answer is (3) T wave.

3. What does the PR interval represent?
(1) Time between atrial and ventricular depolarisation
(2) Ventricular repolarisation
(3) Atrial contraction duration
(4) Total heart cycle time

Explanation: The PR interval measures conduction time from atrial depolarisation onset to ventricular depolarisation onset, including AV nodal delay. It reflects coordinated timing of atrial and ventricular contraction. Correct answer is (1).

4. Assertion (A): QRS complex is larger than P wave.
Reason (R): Ventricles have more muscle mass than atria.
(1) Both A and R true and R explains A
(2) Both A and R true but R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: The QRS complex is larger due to greater ventricular muscle mass, generating higher electrical potential. Both Assertion and Reason are true, and R correctly explains A. Correct answer is (1).

5. Which wave is usually absent or small in ECG recordings?
(1) P wave
(2) Q wave
(3) U wave
(4) T wave

Explanation: U wave is often absent or very small, representing repolarisation of Purkinje fibers. It is not consistently visible. Correct answer is (3) U wave.

6. Which part of ECG corresponds to ventricular contraction?
(1) P wave
(2) QRS complex
(3) T wave
(4) PR interval

Explanation: Ventricular contraction (systole) occurs immediately after the QRS complex, following depolarisation of ventricles. Correct answer is (2) QRS complex.

7. Match ECG components with their events:
a. P wave – i. Ventricular depolarisation
b. QRS complex – ii. Ventricular repolarisation
c. T wave – iii. Atrial depolarisation
(1) a-iii, b-i, c-ii
(2) a-i, b-iii, c-ii
(3) a-ii, b-i, c-iii
(4) a-iii, b-ii, c-i

Explanation: Correct matching: P wave – atrial depolarisation (a-iii), QRS complex – ventricular depolarisation (b-i), T wave – ventricular repolarisation (c-ii). Correct answer is (1).

8. Fill in the blank: The ECG wave representing repolarisation of atria is ______.
(1) P wave
(2) QRS complex
(3) T wave
(4) Usually masked by QRS

Explanation: Atrial repolarisation occurs during ventricular depolarisation and is obscured by the QRS complex in ECG. Correct answer is (4) Usually masked by QRS.

9. Single Correct Answer: The segment between end of QRS and start of T wave is called:
(1) PR segment
(2) ST segment
(3) QT interval
(4) TP segment

Explanation: The ST segment represents the time between ventricular depolarisation and repolarisation. It is important clinically to detect ischemia or infarction. Correct answer is (2) ST segment.

10. Choose the correct statements:
(a) QRS represents ventricular depolarisation
(b) P wave represents atrial depolarisation
(c) T wave represents ventricular repolarisation
(d) U wave is atrial depolarisation
(1) a, b, c only
(2) a, b only
(3) b, c, d only
(4) a, c, d only

Explanation: Correct statements: QRS – ventricular depolarisation (a), P wave – atrial depolarisation (b), T wave – ventricular repolarisation (c). U wave is not atrial depolarisation. Correct answer is (1) a, b, c only.

Subtopic: ABO Blood Group System

• ABO blood group: Classification of human blood based on presence of antigens A and B on red blood cells.

• Gene I: Gene that controls ABO blood group, located on chromosome 9 in humans.

• Alleles: Different forms of a gene; IA, IB, and i are alleles of gene I.

• IA allele: Produces antigen A on red blood cells.

• IB allele: Produces antigen B on red blood cells.

• i allele: Does not produce any antigen, resulting in blood group O.

• Codominance: Both IA and IB alleles express equally when present together.

• Phenotype: Observable characteristic or blood group type (A, B, AB, O).

• Genotype: Genetic composition of alleles (IAIA, IAi, IBIB, IBi, IAIB, ii).

• AB blood group: Result of codominant expression of IA and IB alleles.

• Blood transfusion: Medical process requiring compatible blood groups based on antigens.

Lead Question (2020): Identify the wrong statement with reference to the gene ‘I’ that controls ABO blood groups:
Options:
1. When IA and IB are present together, they express same type of sugar
2. Allele ‘i’ does not produce any sugar
3. The gene (I) has three alleles
4. A person will have only two of the three alleles

Explanation: Correct answer is 1. IA and IB alleles are codominant and express different antigens, not the same. IA produces antigen A, IB produces antigen B. The gene I has three alleles, i does not produce antigen, and an individual inherits only two alleles, one from each parent.

1. Single Correct Answer MCQ:
Which allele of gene I produces no antigen on red blood cells?
Options:
a. IA
b. IB
c. i
d. IAIB

Explanation: Correct answer is c. The i allele does not produce any antigen, resulting in blood group O. IA and IB produce A and B antigens respectively, while IAIB is a genotype representing AB blood group with both antigens expressed.

2. Single Correct Answer MCQ:
AB blood group is an example of:
Options:
a. Complete dominance
b. Codominance
c. Recessive trait
d. Incomplete dominance

Explanation: Correct answer is b. AB blood group results from codominance of IA and IB alleles, both expressed equally, producing A and B antigens on red blood cells.

3. Single Correct Answer MCQ:
A person with genotype IAi will have which blood group?
Options:
a. A
b. B
c. AB
d. O

Explanation: Correct answer is a. IAi genotype produces blood group A. IA is dominant over i, expressing antigen A on red blood cells, while i does not contribute any antigen.

4. Single Correct Answer MCQ:
How many alleles does the gene I have in humans?
Options:
a. Two
b. Three
c. Four
d. One

Explanation: Correct answer is b. The gene I controlling ABO blood groups has three alleles: IA, IB, and i, which combine in pairs to determine an individual's blood group.

5. Single Correct Answer MCQ:
Which blood group results from genotype IBIB?
Options:
a. A
b. B
c. AB
d. O

Explanation: Correct answer is b. IBIB genotype produces blood group B because IB allele produces B antigen on red blood cells, expressed homozygously in this case.

6. Single Correct Answer MCQ:
Blood group O has which genotype?
Options:
a. IAIA
b. IBi
c. ii
d. IAIB